Wlliam Henry Sinclair, Union officer, Freedmen’s Bureau official, state representative, county official, and businessman, was born in Akron, Ohio, on October 31, 1838. He was the son of William and Melissa (Van Hyning) Sinclair and was raised in Jonesville, Michigan. At the outbreak of the Civil War, Sinclair enlisted as a private in Company C of the Seventh Michigan Infantry Regiment. According to an account by his mother, he was a fifer. He received promotions to corporal, sergeant major, and second lieutenant and remained with this unit until September 1861. At that time he was appointed to the First Michigan Light Battery. In 1862 Sinclair transferred to the adjutant general service and accepted a post on the staff of Bvt. Maj. Gen. David S. Stanley in the Army of the Cumberland, where he remained for the remainder of the war. He received promotions to major and assistant adjutant general of volunteers, then brevet colonel in March 1865, and finally full colonel in May 1865. Sinclair earned a reputation as an apt staff officer in the western theater. At the conclusion of the war, he was stationed in Texas at the Federal military headquarters established in Galveston.
In 1866, following the establishment of the Freedmen’s Bureau in Texas, Sinclair received appointment from Texas Bureau head Bvt. Brig. Gen. Edgar M. Gregory, as Assistant General and Subassistant Commissioner for Galveston. In September 1866 Sinclair was mustered out of the army, but he continued his duties, in a civilian capacity, under the designation of “special agent.” In this position, his duties ranged from staff work to inspection tours to oversight of trade and resolution of conflicts associated with Reconstruction efforts. Between 1866 and 1868, he made fourteen tours as acting inspector general and visited nearly every county in southeastern and northern Texas.
As an inspector, Sinclair worked in the areas of the state experiencing the greatest racial, economic, and political strife, and was often forced to intervene in local problems and replace ineffective bureau administrators. Notable examples of such interventions occurred in Brazos, McLennan, and Colorado counties. At the end of 1868, as the Freedman’s Bureau was being phased out in Texas, he lobbied Governor Elisha Pease for its continuation, arguing that it was the only viable means of furthering the goals of Reconstruction. In the spring of 1869 Sinclair returned to Galveston, where he accepted a series of appointments from the Federal military authorities there, including superintendent of education, district clerk, and county treasurer. In the late 1860s, he married Loraine Phoebe Bartholomew in Galveston County. This couple had at least three children, all sons.
In 1870 Sinclair, running under the aegis of the Radical wing of the Republican Party, won election as representative for Galveston County to the Twelfth Texas Legislature. He started his term on February 8, 1870. In this role Sinclair participated in the intra-party quarrels characteristic of the time, and, on May 10, 1871, assumed the position of speaker of the House following the unseating of Representative Ira H. Evans. Sinclair served out his term as speaker on until January 14, 1873.
Following his turn as legislator, Sinclair continued to play a prominent role in Galveston County affairs. He served as revenue collector and postmaster for the Fifth Military District. Additionally, he helped establish electricity, ice manufacturing, and streetcar businesses, as well as founded the Beach Hotel of Galveston. During this time he was active as a Mason and Shriner and was a member of the Military Order of the Loyal Legion of the United States, the Army of Cumberland Association, the Busch Zouaves of Saint Louis, and the Grand Army of the Republic. An avid baseball enthusiast, he headed a group of stockholders to establish a Texas League franchise in Galveston and helped introduce an outfield tally board for fans to keep informed about the scores of other games as well as a promotional Ladies’ Day to boost attendance.
After the death of his wife in 1895, Sinclair left Galveston for a time. He returned to Jonesville, Michigan, and toured the Rocky Mountains. At the end of 1896, Sinclair traveled to New York to assist in a road-building venture. He died in Rochester, New York, on January 11, 1897. He was buried in Galveston at Lakeview Cemetery on January 17.