1822 Boundary Lines The Washtenaw County boundary lines were established on September 10 by the Legislative Council, but the land area was attached to Wayne County, Territory of Michigan, for administration.

1823 Settlement About a mile southeast of Ypsilanti, Benjamin Woodruff began the first permanent European settlement.

1824 Allen Cabin The first cabin in what is now Ann Arbor was built near Allen Creek by Elisha W. Rumsey and John Allen during Spring of this year. Later in the year Ann Arbor was selected as the seat for County government. It is reported that there were 15-30 settlers in the "County" at that time..

1825 Public Services Post Office was established and John Allen became the Postmaster. The first school was a log building in Ann Arbor and Miss Monroe taught the classes. Old Chicago Road, the first public road in the County, was surveyed. This road, for the most part, followed the Detroit to Chicago Indian Trail.

1826 Formal Organization During the year the requirements for legally organizing into an independent county took place.

1827 County Established On January 1, Washtenaw County, Territory of Michigan, legally came into being. Division of the County into 20 townships began later that year. The population was nearly 1,000. The first session of County Court was held in the home of Erastus Priest by Samuel W. Dexter, Chief Justice; and by Oliver Whitmore, Associate Justice. The Legislative Council approved the first Circuit Court on April 13, and a Probate Judge was appointed. Marriages recorded.

1828 Circuit Court In November, the first session of Circuit Court was held by Honorable William Woodbridge.

1829 County Jail A jail was the first public County building to be constructed. The first newspaper, "The Western Emigrant" a five column folio, edited by Thomas Simpson, was published on November 18th, in Ann Arbor.

1833 Naturalization Filing of naturalization information began.

1834 Courthouse The County was seven years of age when construction of the first Courthouse was completed.

1969 County Commissioners The Board of County Supervisors, composed of one representative from each Township and two or more persons from each City, was replaced by a smaller Board of Commissioners. Each Commissioner represented one of 13 districts into which the County was divided. Following the 1970 Census, Commissioner districts were increased in number to keep the population per district at approximately the previous level: the result, 15 districts.