Mountrail County was first
established in 1873 (as Mountraille County) by the Dakota Territorial
Legislature. The boundaries extended from the Missouri River north to
the border with Canada. It remained a county when North Dakota became
a state in 1889, but in 1892 North Dakota Legislature authorized
neighboring Ward County to take over all of Mountrail's territory,
and this county was eliminated.
At the November 3, 1908, general election,
a vote was held in Ward County on whether to recreate Mountrail with different
boundaries. The vote was 4,207 to 4,024 in favor of the new county, but
North Dakota's Attorney General sued the Secretary of State over
the validity of the vote. Organization of the new Mountrail County was delayed
until the Supreme Court affirmed the vote in January 1909