As of the 2010 census, the city population was 8,521. The city is surrounded on three sides by Tecumseh Township, but is politically independent. Raisin Township borders the southern edge of the city. The city was rated #93 in 2009, as one of 100 of the best small towns to live in by CNNMoney.com.
The boundaries of Lenawee County were laid out by a proclamation of the Territorial Governor, Lewis Cass on September 10, 1822. Lenawee remained attached to Monroe County, out of which it was formed, until an act of the Territorial Legislature passed on December 26, 1826, organized the county government. The first settlement in the county was made two years earlier, on May 21, 1824, in Tecumseh. The settlers, consisting of fifteen men, eleven women, and six children, all came from Jefferson County, New York. In 1823, Musgrove Evans had located the land and persuaded General Joseph W. Brown and the others to move to the site. Brown and Evans, along with Austin Eli Wing purchased land there and platted the village of Tecumseh in 1824. These founders appealed to Governor Cass to locate the county seat of Lenawee at Tecumseh. This was accomplished by an act of the Territorial Legislature on June 30, 1824, even though county government would not be organized for another year and a half. Tecumseh would remain the county seat until 1838, when it was transferred to Adrian. The Township of Tecumseh was organized on April 12, 1837, initially encompassing the entire northern third of the county.
Among the noteworthy events which have occurred in Tecumseh is the world famous Dynamic Kernels tithing project. A local mill owner, Perry Hayden, planted a cubic inch of wheat and donated 10% of the harvest to the church and replanted the remainder. He continued this for the following 6 years, resting on the 7th. The amount of land needed for the final crop exceeded . Henry Ford donated much of the necessary land as did many local farmers. The project received much attention including a feature in Life magazine on July 24, 1944. In 2008 Tecumseh Friends Church now called Riverbend Friends Church began the Dynamic Kernels Project again. Their goal, like that of Mr. Hayden, is to inspire people to a renewed sense of what God can do in their lives. To tithe not only their money but their entire life to God's service.
A horse, Don Juan, that belonged to the General George Armstrong Custer is buried in Tecumseh, the horse having been sent to a friend living there after the General's death.
The two deadliest mass murderers in the USA lived in Tecumseh, Michigan. Andrew Phillip Kehoe was born and raised in Tecumseh, Michigan and then moved to Bath, Michigan and perpetrated the deadliest act of violence in an educational setting in the USA. On May 18, 1927, Kehoe killed his wife and then blew up the school building in Bath, Michigan with dynamite. 38 elementary school children and 6 adults were killed and another 58 injured. The event is named the Bath School Disaster. Tecumseh is also where Henry Lee Lucas killed his mother and then became what may be the most severe serial killer. Lucas confessed to killing over 600 people, but authorities believe that he could not have killed more than 213.
One of the village's most well-known manufacturers was Tecumseh Products. Founded by the Herrick family during the early part of the 20th century, Tecumseh Products initially began business manufacturing refrigeration compressors. The company moved out of Tecumseh in 2008, moving the remaining production to a plant in Tupelo, Mississippi, and its headquarters to Pittsfield Township, Michigan, just outside Ann Arbor, Michigan.
Consolidated Biscuit Company of McComb, Ohio, agreed to buy the Products plant in 2008, pending an environmental review.