The history of Lexington Township starts with the passage of two pieces of legislation. The first piece of legislation was the Land Ordinance of 1785 that provided for the sale and survey of public lands west of the Appalachians, north of the Ohio River and east of the Mississippi River. It also created a system which divided the land into townships. The other is the Northwest Ordinance of 1787 which created a style of government for these territories and a method for these territories to become states.
From 1787 to 1803, Michigan was a part of the Northwest Territory. Then from 1803 until 1805, Michigan was part of the Indiana Territory. But, in 1805, Michigan was separated from Indiana and became a territory in its own right.
With the end of the War of 1812, the Indian problems ended and British involvement in the fur trade stopped, pioneers began to pour into the Northwest Territory. This resulted in new states being created, first Ohio and then Indiana. When Indiana was admitted into the union in 1816, Michigan was allowed to become a territory, with government established at Detroit. This also resulted in a baseline (east and west) and a meridian line (north and south) being established to survey for the creating of townships. In 1822, Sanilac County was laid out and was attached to Oakland County. The first mention of Sanilac County in official records is in the Territorial Laws of 1827. A special act attached it to St. Clair County for judicial purposes.
On January 26, 1837, President Andrew Jackson made Michigan a state and in the same year Lexington Township was organized, making it the oldest township in the county. Sanilac County also at that time included all of what is now Sanilac, Huron, and Tuscola counties. An act of legislature on December 3, 1848, authorized the organization of Sanilac County as a separate county with Lexington as the county seat. Lexington Township at this time included all of the present day townships of Worth, Sanilac, Buel and Elk.
The two municipalities within Lexington Township are the Village of Lexington and the city of Croswell. The Village and the Township grew up together. Lexington was the county seat and a major lake port until the county seat was moved to Sandusky in 1880. The railroad coming to Croswell in 1879 turned that city into an important farm center for the area. The great fires of 1871 and 1881 did not do a lot of damage to the township, although it did end the lumbering era for the area. The historic storm of 1913 took out all the major docks in Lexington. After which the building of the sugar and canning factories, along with the railroad made Croswell into an economic center for the township.
In the first half of the 20th century, agriculture, commercial fishing, and tourism were the major sources of income for the people of the township. The automobile and better roads were changing the face of the township. By the end of World War II, the area along the Lake Huron Shore was a mecca for summer tourism.
Lexington Township also housed the Sanilac County Poor Farm built in 1868 and closed in 1958.
At the end of World War II, Croswell housed three separate German Prisoner of War camps. They helped with the farming and worked in the factories. They helped eased the U.S. Military cost of their care.