Okla. Stat. tit. 69 § 653
The State Highway Department shall numerically designate each section line in the State of Oklahoma according to the following system:
The first section line running north and south at the west end of the State shall be designated NS1, each succeeding section line shall have the number changed in numerical order, the prefix NS remaining the same, until a number has been assigned to the last section line paralleling the Arkansas border. In like manner the first section line running east and west below the northern border of Oklahoma shall be designated EW1 and each succeeding section line shall be changed in numerical sequence, the prefix EW remaining the same until the last section line north of the Red River has been designated.
Okla. Stat. tit. 69, § 653