Okla. Stat. tit. 69 § 1301
The provisions of this article, except those provisions authorizing the use of special assessments, shall extend to the State of Oklahoma through the Commission, and to every city in this state having a population of two thousand (2,000) or more, according to the last preceding Federal Decennial Census, whether such city is or shall hereafter be operating under a charter form of government or under general law. The provisions of this article authorizing the use of special assessments shall extend to very county of the state having a population of forty-two thousand (42,000) or more, in which there is located a city having a population in excess of twenty-seven thousand (27,000) as shown by the last preceding Federal Decennial Census, and the provisions of this article authorizing the use of special assessments shall extend to every city in this state having a population in excess of twenty-seven thousand (27,000) as shown by the last preceding Federal Decennial Census.
Okla. Stat. tit. 69, § 1301