History Isabella County was described by action of the Michigan Territory legislature in 1831, but for purposes of population, revenue, and judicial matters, it was assigned to nearby counties. Its area was partitioned from unorganized territory plus a portion of Mackinac, which had existed as a Territorial County since 1818.
History Isabella County was described by action of the Michigan Territory legislature in 1831, but for purposes of population, revenue, and judicial matters it w.as assigned to nearby counties Its area was partitioned from unorganized territory plus a portion of Mackinac, which had existed as .a ,Territorial County since 1818