Okla. Stat. tit. 61, § 6

In the construction of all public buildings erected for the state, or for any county thereof, where the expense of construction is borne wholly or in part by the state, or county, by appropriation, by the issuance of bonds, or by taxation, preference shall be given to materials mined, quarried, manufactured or procured within the State of Oklahoma, provided that the same can be procured at no greater expense than like material or materials of equal quality from without the state. Laws 1910-11, c. 76, p. 174, § 1.