Originally an Indian village and trading post called Indian Mills.

Isabella City was the first county seat until 1860. Located 2 miles north of Mt. Pleasant, on the Chippewa River. G.F. Grinnell, was the postmaster. A bronze plaque mounted on a large rock on Old U.S. 27 marks the spot.
Placed there by the Isabella County D.A.R.

Longwood was established on February 30, 1871 by Major James W. Long and John P. Hawkins. It was located on the northwest quarter of the northwest quarter of section 11 of Union township, and just across the Chippewa river from Isabella City. Not much was done by the Major to establish a city. He did, however, build a small factory for the making of "Monarch Bitters" and at one time offered to do something toward the building of a court house for the county, provided the county seat would be moved to his burg. The people did not seem to take kindly to the proposition and the scheme failed for want of cheerful support. And soon after the Major moved all of his buildings and belongings to Mt. Pleasant and became a part of the city, erecting a very large hotel on the spot now occupied by the commercial block (1911 – Fancher).