Texas Local Government Code - LOC GOV'T § 324.121. Annexation

(a) The voters of an unincorporated area that is contiguous to a district may file a petition with the board to annex the area to the district.

(b) The petition must contain an accurate description of the area proposed for annexation, accompanied by an accurate map or plat of the area.

(c) The petition must be signed by at least one percent of the registered voters in the area proposed for annexation.

(d) If the board considers the proposed annexation desirable, the board shall file the petition with the commissioners court with a statement of the reasons the board favors the annexation.

(e) The commissioners court shall give notice of a hearing on the petition and hold a hearing in the manner prescribed by Sections 324.022 and 324.023 for a petition for creation of a district.

(f) The commissioners court may grant the petition if it finds the petition meets the requirements of this section and the annexation promotes the purposes for which the district was created.