SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

o

Rule 13d-1(b)

x

Rule 13d-1(c)

o

Rule 13d-1(d)

CUSIP No. 903293405

13G

Page 2 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
V. PREM WATSA

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
CANADIAN

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,694,554

7

Sole Dispositive Power

8

Shared Dispositive Power
1,694,554

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,694,554

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
IN

CUSIP No. 903293405

13G

Page 3 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
1109519 ONTARIO LIMITED

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
ONTARIO, CANADA

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,694,554

7

Sole Dispositive Power

8

Shared Dispositive Power
1,694,554

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,694,554

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 4 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
THE SIXTY TWO INVESTMENT COMPANY LIMITED

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
BRITISH COLUMBIA, CANADA

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,694,554

7

Sole Dispositive Power

8

Shared Dispositive Power
1,694,554

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,694,554

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 5 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
810679 ONTARIO LIMITED

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
ONTARIO, CANADA

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,694,554

7

Sole Dispositive Power

8

Shared Dispositive Power
1,694,554

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,694,554

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 6 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
FAIRFAX FINANCIAL HOLDINGS LIMITED

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
CANADA

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,694,554

7

Sole Dispositive Power

8

Shared Dispositive Power
1,694,554

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,694,554

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 7 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
ODYSSEY REINSURANCE COMPANY

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
CONNECTICUT

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
1,604,912

7

Sole Dispositive Power

8

Shared Dispositive Power
1,604,912

9

Aggregate Amount Beneficially Owned by Each Reporting Person
1,604,912

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
1.2%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 8 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
NORTHBRIDGE GENERAL INSURANCE CORPORATION

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
CANADA

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
32,800

7

Sole Dispositive Power

8

Shared Dispositive Power
32,800

9

Aggregate Amount Beneficially Owned by Each Reporting Person
32,800

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
0.1%

12

Type of Reporting Person
CO

CUSIP No. 903293405

13G

Page 9 of 21 Pages

1

Names of Reporting Person/I.R.S. Identification Nos. of Above Persons (Entities Only)
UNITED STATES FIRE INSURANCE COMPANY

2

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

x

3

SEC Use Only

4

Citizenship or Place of Organization
DELAWARE

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5

Sole Voting Power

6

Shared Voting Power
10,000

7

Sole Dispositive Power

8

Shared Dispositive Power
10,000

9

Aggregate Amount Beneficially Owned by Each Reporting Person
10,000

10

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares  o

11

Percent of Class Represented by Amount in Row 9
0.1%

12

Type of Reporting Person
CO

Item 1. (a)

Name of Issuer:
USG Corporation

Item 1(b)

Address of Issuer’s Principal Executive Offices:
550 West Adams Street, Department 188, Chicago, Illinois 60661

Item 2. (a)

Name of Person Filing:
This statement is being jointly filed by the following persons (collectively, the “Reporting Persons”):

1.   V. Prem Watsa, an individual;

2.   1109519 Ontario Limited (“1109519”), a corporation incorporated under the laws of Ontario;

3.   The Sixty Two Investment Company Limited (“Sixty Two”), a corporation incorporated under the laws of British Columbia;

4.   810679 Ontario Limited (“810679”), a corporation incorporated under the laws of Ontario;

5.   Fairfax Financial Holdings Limited (“Fairfax”), a corporation incorporated under the laws of Canada;

6.   Odyssey Reinsurance Company (“Odyssey”), a corporation incorporated under the laws of Connecticut;

7.   Northbridge General Insurance Corporation (“Northbridge”), a corporation incorporated under the laws of Canada; and

8.   United States Fire Insurance (“US Fire”), a corporation incorporated under the laws of Delaware.

Item 2(b)

Address of Principal Business Office:
The addresses of the Reporting Persons are as follows:

1.   Mr. Watsa’s business address is 95 Wellington Street West, Suite 800, Toronto, Ontario M5J 2N7;

2.   The principal business address and principal office address of 1109519 is 95 Wellington Street West, Suite 800, Toronto, Ontario M5J 2N7;

3.   The principal business address and principal office address of Sixty Two is 1600 Cathedral Place, 925 West Georgia St., Vancouver, British Columbia V6C 3L3;

4.   The principal business address and principal office address of 810679 is 95 Wellington Street West, Suite 800, Toronto, Ontario M5J 2N7;

5.   The principal business address and principal office address of Fairfax is 95 Wellington Street West, Suite 800, Toronto, Ontario M5J 2N7;

6.   The principal business address and principal office address of Odyssey is 300 First Stamford Place, Stamford, Connecticut 06902;

7.   The principal business address and principal office address of Northbridge is 105 Adelaide Street West, 3rd Floor, Toronto, Ontario, Canada M5H 1P9; and

8.   The principal business address and principal office address of US Fire is 305 Madison Avenue, Morristown, New Jersey 07962.

Item 2(c)

Citizenship:
V. Prem Watsa is a citizen of Canada.

Item 2(d)

Title of Class of Securities:
Common Stock

Item 2(e)

CUSIP Number:
903293405

Item 3.

If this statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) or (c), check whether the person filing is a:

(a)

o

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)

o

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)

o

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

o

A parent holding company or control person, in accordance with §240.13d-1(b)(1)(ii)(G);

(h)

o

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

A non-US institution in accordance with §240.13d-1(b)(1)(ii)(J);

(k)

o

Group, in accordance with §240.13d-1(b)(1)(ii)(K).

Item 4.

Ownership.

Based on the most recent information available, the aggregate number and percentage of the shares of common stock (the “Shares”) of USG Corporation that are beneficially owned by each of the Reporting Persons is set forth in boxes 9 and 11 of the second part of the cover page to this Schedule 13G, and such information is incorporated herein by reference.

The number of Shares as to which each of the Reporting Persons has sole voting power, shared voting power, sole dispositive power and shared dispositive power is set forth in boxes 5, 6, 7 and 8, respectively, on the second part of the cover page to this Schedule 13G, and such information is incorporated herein by reference.

Shares reported as beneficially owned include Shares issuable upon conversion of certain convertible debt securities of USG Corporation.

Neither the filing of this Schedule 13G nor the information contained herein shall be deemed to constitute an affirmation by V. Prem Watsa, 1109519, Sixty Two, 810679, Fairfax, Odyssey, Northbridge or US Fire that such person is the beneficial owner of the Shares referred to herein for purposes of Section 13(d) or 13(g) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed.

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following x.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company.

Not applicable.

Item 8.

Identification and Classification of Members of the Group.

See attached Exhibit No. 1.

Item 9.

Notice of Dissolution of Group.

Not applicable.

Item 10.

Certification.

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Dated: February 14, 2014

V. Prem Watsa

/s/ V. Prem Watsa

Dated: February 14, 2014

1109519 Ontario Limited

By:

/s/ V. Prem Watsa

Name: V. Prem Watsa

Title:  President

Dated: February 14, 2014

The Sixty Two Investment Company

Limited

By:

/s/ V. Prem Watsa

Name: V. Prem Watsa

Title:  President

Dated: February 14, 2014

810679 Ontario Limited

By:

/s/ V. Prem Watsa

Name: V. Prem Watsa

Title:  President

Dated: February 14, 2014

Fairfax Financial Holdings Limited

By:

/s/ Paul Rivett

Name: Paul Rivett

Title:  President

Dated: February 14, 2014

Odyssey Reinsurance Company

By:

/s/ Kirk M. Reische

Name: Kirk M. Reische

Title:  Vice President

Dated: February 14, 2014

Northbridge General Insurance Corporation

By:

/s/ Craig Pinnock

Name: Craig Pinnock

Title:  CFO

Dated: February 14, 2014

United States Fire Insurance Company

By:

/s/ James V. Kraus

Name:

James V. Kraus

Title:

Senior Vice President, General
Counsel and Secretary

Exhibit No.

Description

1

Members of filing group.

2

Joint Filing Agreement dated as of February 14, 2014 among V. Prem Watsa, 1109519 Ontario Limited, The Sixty Two Investment Company Limited, 810679 Ontario Limited, Fairfax Financial Holdings Limited, Odyssey Reinsurance Company, Northbridge General Insurance Corporation and United States Fire Insurance Company.