Mont. Code Ann. § 70-28-201

Whenever the government of the United States has granted lands in the state of Montana to the heirs of a deceased entryman, any person who claims an estate of inheritance or interest in the lands may bring and maintain an action in rem against all the world in the district court for the county in which the real property is situated to establish the person's title to the property and to determine all adverse claims to the title. Any number of separate parcels of land claimed by the plaintiff may be included in the same action.