EXHIBIT 32.1

SECTION 1350 CERTIFICATION BY THE CHIEF EXECUTIVE OFFICER

I, Timothy W. Byrne, Chief Executive Officer of United States Lime & Minerals, Inc. (the “Company”), hereby certify that, to my knowledge:

(1) The Company’s Annual Report on Form 10-K for the year ended December 31, 2019 (the “Form 10-K”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2) The information contained in the Form 10-K fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: February 28, 2020	/s/ TIMOTHY W. BYRNE
	Timothy W. Byrne
	President and Chief Executive Officer