Okla. Stat. tit. 69 § 606
The board of county commissioners of any two or more adjoining counties may unite in the construction of a bridge, or bridges, over any stream forming the boundary line between such counties or flowing from one county into the other, and the said bridge, or bridges, may be located by them at any point or points on the stream not more than two (2) miles from the boundary line of the counties. If the board of county commissioners of each county so situated finds that a bridge across the stream is necessary and approves its construction, it shall be the duty of the boards of county commissioners, and each of them, to at once proceed with the construction of the bridge. Such counties shall bear the cost of the construction of the bridge, or bridges as agreed by said counties; such construction shall be under the supervision of the boards of county commissioners, which boards shall act in conjunction in such construction; and the bridge, when so constructed, shall remain the property of such counties, respectively, and shall be jointly maintained by such counties.
Okla. Stat. tit. 69, § 606