Montana Code Annotated · § 7-2-4208 — Annexation across county boundaries

(1) Except as provided in subsection (2), in all instances of annexation allowed under parts 42 through 47 of this chapter, a municipal governing body may not annex territory in a county that is different from the county in which the municipality is located.

(2) Annexation by a municipality of territory in a county that is different from the county in which the municipality is located may occur only if the municipality and the county execute an interlocal agreement that provides for a joint city-county planning board and jurisdictional equality.