Colonel Robert P. Sinclair (b. October 17, 1814 in Romulus, Seneca Co., NY; d. ca. 1886 in Grand Rapids, Michigan.) was in command of the 14th Regiment Michigan Infantry when it mustered out of Ypsilanti on 13 February 1862 with an enrollment of 925 officers and men.
Robert's brother William M. Sinclair owned the Sinclair Mills in Ann Arbor.
More information
http://familytreemaker.genealogy.com/users/k/i/c/Kendall-Kic-PA/WEBSITE-0001/UHP-0116.html
