As filed with the U.S. Securities and Exchange Commission on March 7, 2018

File Nos. 333-179904 and 811-22649

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☒
Post-Effective Amendment No. 370	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 370	☒

(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.	DEEPA DAMRE, ESQ.
WILLKIE FARR & GALLAGHER LLP	BLACKROCK FUND ADVISORS
787 SEVENTH AVENUE	400 HOWARD STREET
NEW YORK, NY 10019-6099	SAN FRANCISCO, CA 94105

It is proposed that this filing will become effective (check appropriate box):

☐ Immediately upon filing pursuant to paragraph (b)

☒ On March 9, 2018, 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)

If appropriate, check the following box:

☒ The post-effective amendment designates a new effective date for a previously filed post-effective amendment.

Explanatory Note

This Post-Effective Amendment No. 370 to the Registrant’s Registration Statement on Form N-1A is being filed pursuant to paragraph (b)(1)(iii) of Rule 485 of the Securities Act of 1933, as amended (the “1933 Act”), solely for the purpose of delaying, until March 9, 2018, the effectiveness of the registration statement for the iShares Evolved U.S. Financials ETF (the “Fund”), filed in Post-Effective Amendment No. 306 on November 16, 2017, pursuant to paragraph (a) of Rule 485 of the 1933 Act.

The effectiveness of the Registration Statement of the Fund was previously delayed pursuant to paragraph (b)(1)(iii) of Rule 485 of the 1933 Act as follows:

PEA No.	Date Filed	Automatic Effective Date
325	January 29, 2018	February 12, 2018
338	February 9, 2018	February 20, 2018
346	February 16, 2018	February 23, 2018
354	February 22, 2018	March 2, 2018
362	March 2, 2018	March 7, 2018

This Post-Effective Amendment No. 370 incorporates by reference the information contained in Parts A, B and C of Post-Effective Amendment No. 306.

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)(1)(iii) of the Securities Act of 1933, as amended, and has duly caused this Post-Effective Amendment No. 370 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 7^th day of March, 2018.

iSHARES U.S. ETF TRUST
By:
	Martin Small*
	President
	Date: March 7, 2018

Pursuant to the requirements of the Securities Act of 1933, as amended, this Post-Effective Amendment No. 370 to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated.

By:
	Mark K. Wiedman*
	Trustee
	Date: March 7, 2018
	John E. Martinez*
	Trustee
	Date: March 7, 2018
	Cecilia H. Herbert*
	Trustee
	Date: March 7, 2018
	Charles A. Hurty*
	Trustee
	Date: March 7, 2018
	John E. Kerrigan*
	Trustee
	Date: March 7, 2018

	Robert S. Kapito*
	Trustee
	Date: March 7, 2018
	Madhav V. Rajan*
	Trustee
	Date: March 7, 2018
	Jane D. Carlin*
	Trustee
	Date: March 7, 2018
	Drew E. Lawton**
	Trustee
	Date: March 7, 2018
	Richard L. Fagnani**
	Trustee
	Date: March 7, 2018
	/s/ Jack Gee
	Jack Gee*
	Treasurer and Chief Financial Officer
	Date: March 7, 2018
* By:	/s/ Jack Gee
	Jack Gee
	Attorney-in-fact
	Date: March 7, 2018

* Powers of Attorney, each dated October 15, 2016, for Martin Small, Jane D. Carlin, Mark K. Wiedman, Charles A. Hurty, Cecilia H. Herbert, John E. Kerrigan, John E. Martinez, Madhav V. Rajan, Robert S. Kapito and Jack Gee are incorporated herein by reference to Post-Effective Amendment No. 236, filed November 15, 2016.

** Powers of Attorney, each dated June 21, 2017, for Drew E. Lawton and Richard L. Fagnani are incorporated herein by reference to Post-Effective Amendment No. 298, filed November 1, 2017.