Exhibit 5.1

[Letterhead of Barack Ferrazzano Kirschbaum & Nagelberg LLP]

May 17, 2012

Heartland Financial USA, Inc.

1398 Central Avenue

Dubuque, Iowa 52001

Ladies and Gentlemen:

We have acted as special counsel to Heartland Financial USA, Inc., a Delaware corporation (the “Company”), in connection with the registration under the Securities Act of 1933, as amended (the “Securities Act”), of 500,000 shares (the “Shares”) of common stock, $1.00 par value per share, of the Company (“Common Stock”), pursuant to the Heartland Financial USA, Inc. 2012 Long-Term Incentive Plan (the “Plan”), as set forth in the Registration Statement on Form S-8 to be filed with the Securities and Exchange Commission (the “Commission”) on or about May 17, 2012 (the “Registration Statement”). Capitalized terms used, but not defined, herein shall have the meanings given such terms in the Registration Statement. This opinion is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

We have examined and relied upon the originals, or copies certified or otherwise identified to our satisfaction, of such records, documents and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. In our investigation, we have assumed the genuineness of all signatures, the proper execution of all documents submitted to us as originals, the conformity to the original documents of all documents submitted to us as copies and the authenticity of the originals of such copies. We have also assumed the legal capacity of all natural persons, the genuineness of the signatures of persons signing all documents in connection with which this opinion is rendered, the authority of such persons signing on behalf of the parties thereto other than the Company and the due authorization, execution and delivery of all documents by the parties thereto other than the Company. We have not independently established or verified any facts relevant to the opinions expressed herein, but have relied upon statements and representations of officers and other representatives of the Company.

Based upon the foregoing, but assuming no responsibility for the accuracy or the completeness of the data supplied by the Company and subject to the qualifications, assumptions and limitations set forth herein, it is our opinion that the Shares have been duly authorized and, when the Registration Statement becomes effective and the Shares have been issued in accordance with the Plan, the Shares will be validly issued, fully paid and nonassessable.

Our opinion set forth above is subject to: (i) the effect of bankruptcy, insolvency, reorganization, fraudulent transfer, moratorium or other similar laws relating to or affecting the rights and remedies of creditors; and (ii) the effect of general principles of equity, whether considered in a proceeding in equity or at law (including the possible unavailability of specific performance or injunctive relief), concepts of materiality, reasonableness, good faith and fair dealing, and the discretion of the court before which a proceeding is brought. We express no opinion as to waivers of broadly or vaguely stated rights.

We express no opinion concerning the laws of any jurisdiction other than the federal law of the United States of America and the Delaware General Corporation Law. We express no opinion as to the laws of any other jurisdiction and no opinion regarding the statutes, administrative decisions, rules, regulations or requirements of any county, municipality, subdivision or local authority of any jurisdiction.

This opinion is being furnished to you solely for your benefit in connection with the transactions set forth above. It may not be relied upon by, nor a copy of it delivered to any other party, without our prior written consent. This opinion is based upon our knowledge of the law and facts as of the date hereof, and we assume no duty to communicate with you with respect to any matter that comes to our attention hereafter (even though such matter may affect any legal conclusion stated in this opinion letter).

We consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. In giving the foregoing consent, we do not thereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act of 1933, or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Barack Ferrazzano Kirschbaum & Nagelberg LLP

BARACK FERRAZZANO KIRSCHBAUM & NAGELBERG LLP