As filed with the U.S. Securities and Exchange Commission on February 28, 2015

Securities Act File No. 333-179904

Investment Company Act File No. 811-22649

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	x
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 149	x
and/or
REGISTRATION STATEMENT
UNDER
THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 149	x

(Check appropriate box or boxes)

iShares U.S. ETF Trust

(Exact Name of Registrant as Specified in Charter)

c/o State Street Bank and Trust Company

1 Iron Street

Boston, MA 02210

(Address of Principal Executive Office)(Zip Code)

Registrant’s Telephone Number, including Area Code (415) 670-2000

The Corporation Trust Company

1209 Orange Street

Wilmington, DE 19801

(Name and Address of Agent for Service)

With Copies to:

MARGERY K. NEALE, ESQ.
WILLKIE FARR &
GALLAGHER LLP
787 SEVENTH AVENUE
NEW YORK, NY 10019-6099 BENJAMIN J. HASKIN, ESQ.
WILLKIE FARR &
GALLAGHER LLP
1875 K STREET, N.W.
WASHINGTON, D.C. 20006-1238 EDWARD BAER, ESQ. BLACKROCK FUND ADVISORS 400 HOWARD STREET SAN FRANCISCO, CA 94105

Continuous

(February 28, 2015)

It is proposed that this filing will become effective:

x immediately upon filing pursuant to paragraph (b)

¨ on (date) pursuant to paragraph (b)

¨ 60 days after filing pursuant to paragraph (a)(1)

¨ on (date) pursuant to paragraph (a)(1)

¨ 75 days after filing pursuant to paragraph (a)(2)

¨ on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

¨ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

This filing relates solely to the following Fund, a series of iShares U.S. ETF Trust:

iShares Short Maturity Municipal Bond ETF

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all the requirements for the effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Post-Effective Amendment No. 149 to the Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of San Francisco and the State of California on the 27^th day of February, 2015.

iSHARES U.S. ETF TRUST

By:
	Manish Mehta*
	President
	Date: February 27, 2015

Pursuant to the requirements of the Securities Act of 1933, as amended, this Post-Effective Amendment No. 149 to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated.

Mark Wiedman*

Trustee

Date: February 27, 2015

John E. Martinez*

Trustee

Date: February 27, 2015

Cecilia H. Herbert*

Trustee

Date: February 27, 2015

Charles A. Hurty*

Trustee

Date: February 27, 2015

John E. Kerrigan*

Trustee

Date: February 27, 2015

Robert H. Silver*

Trustee

Date: February 27, 2015

Robert S. Kapito*

Trustee

Date: February 27, 2015

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	Madhav V. Rajan*
	Trustee
	Date: February 27, 2015
	/s/ Jack Gee
	Jack Gee
	Treasurer
	Date: February 27, 2015
*By:	/s/ Jack Gee
	Jack Gee
	Attorney-in-fact
	Date: February 27, 2015

* Powers of Attorney, each dated December 31, 2013, for Manish Mehta, Mark Wiedman, Charles A. Hurty, Cecilia H. Herbert, John E. Kerrigan, Robert H. Silver, John E. Martinez, Madhav V. Rajan and Robert S. Kapito are incorporated herein by reference to Post-Effective Amendment No. 46, filed January 10, 2014.

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EXHIBIT INDEX

Index No.	Description of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

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