Settlement of DeWitt Township began with the arrival of Captain David Scott and his family from Ann Arbor on October 4, 1833. The State Legislature formally created the Township on March 23, 1836. The first Township meeting was held at the house of Captain Scott on April 8, 1836. A gentleman by the name of Welcome J. Partelo was named the Township's first Supervisor at that meeting.
It did not take long for the state to divide DeWitt Township into the many townships that we recognize today. In 1837, the Township was split in half by a North/South line with the western half becoming Watertown Township. Two years later, the Township was again split in half by an East/West line with the northern half becoming Bingham Township. One day later, the Governor approved an act, which split the remaining Township area in half by a North/South line with the eastern half becoming Ossowa Township (renamed Bath Township in 1843). The final split of the Township came in 1841 with the northern half of the remaining land becoming Olive Township. In four short years, DeWitt Township went from encompassing the entire County to its current boundary.
The county seat for Clinton County was also located in DeWitt Township from the inception of the County. The county seat remained in DeWitt Township until December 1857 when it was moved to Plumstead Hall, in the Village of St. Johns, until a new courthouse could be built.
The Township became a Charter Township on November 7, 1978.