Okla. Stat. tit. 19 § 901.22
Any territory located within the same county of an existing district may be included in the limits of such district by decision of the board of directors, certified to the board of county commissioners, with the written consent of twenty-five percent (25%) of the holders of title to the territory sought to be included, or in the same manner as provided for the organization of fire protection districts. Such territory shall not be included or added to the territory of the district without the consent of the board of directors and the board of county commissioners. In the event such territory is included by decision of the board of directors, with the consent of the board of county commissioners and the written consent of twenty-five percent (25%) of the holders of title to the territory sought to be included, the notice, hearing and order requirements of Section 901.2 of this title and the notice and election requirements of Sections 901.3 and 901.4 of this title shall be followed in the same manner as for the organization of fire protection districts. In case any such territory is added to the district the property therein shall immediately become subject to the lien for the payment of bonds theretofore authorized by the district in the same manner as property within the district at the time of authorization of such bonds.
Any territory adjacent to the existing district but within another county may be included in the limits of such district by decision of the board of directors, certified to the board of county commissioners of both counties, with the written consent of twenty-five percent (25%) of the holders of title to the territory sought to be included, or in the same manner as provided for the organization of fire protection districts. Such territory shall not be included or added to the territory of the district without the consent of the board of directors and the board of county commissioners of each county. In the event such territory is included by decision of the board of directors, with the consent of the board of county commissioners of each county and the written consent of twenty-five percent (25%) of the holders of title to the territory sought to be included, the notice, hearing and order requirements of Section 901.2 of this title and the notice and election requirements of Sections 901.3 and 901.4 of this title shall be followed in the same manner as for the organization of fire protection districts. In case any such territory is added to the district the property therein shall immediately become subject to the lien for the payment of bonds theretofore authorized by the district in the same manner as property within the district at the time of authorization of such bonds.
Any landowner whose property is within the response area of the district as assigned by the county commissioners but is not within the fire protection district itself may elect to opt into the district by paying the assessment to the district. The landowner then becomes a member of the district with full voting rights.
Okla. Stat. tit. 19, § 901.22