Okla. Stat. tit. 19, § 19-294: Duty to index old records

The register of deeds of any county of this state shall, in

addition to the duties now prescribed by law, make and keep indexes

in the same manner as is now provided by Sections 1733 and 1737 of

Snyder's Compiled Laws, 1909, of all records, files, books,

instruments, or the certified copy thereof, pertaining to the title

to lands in such county, which were of record in the office of

United States Court, or any office maintained by the United States

prior to November 16, 1907, for filing and recording deeds,

mortgages, liens and other instruments which have been, or may

hereafter be, received by such register of deeds.