John Gibson Parkhurst was born April 17, 1824 in Oneida Castle, New York. He received his education at Oneida Academy and after being accepted into the bar, rode the circuit court in New York. In 1848 he moved to Coldwater, Michigan where he continued his law practice. In 1860 he began his political career as secretary to the ill-fated Democratic Convention that met in Charleston, South Carolina. Parkhurst had two daughters, Margaret and Kate Amelia ("Kittie"). His wife, Amelia, died on July 26, 1861.

When the Civil War broke out he enlisted as Lieutenant Colonel in the Ninth Michigan Infantry Regiment, the first Michigan regiment to enter active service in the Western Department. On July 13, 1862 a detachment of the regiment was attacked at Murfreesboro by a Confederate force under Nathan Bedford Forrest. After a sharp fight, Parkhurst and his men were forced to surrender. He was exchanged in December 1862 and was commissioned as Colonel of the regiment on February 6, 1863. For the remainder of the war, the Ninth Regiment served as Provost Guard in the Army of the Cumberland seeing action at the battles of Stones River, Chickamaugua, and the Atlanta Campaign. Parkhurst received successive promotions to Provost Marshall for the 14th Army Corps and Provost Marshall for the Military District of Tennessee. On May 22, 1865 he was appointed Brevit Brigadier General "for gallant, faithful, and mentorious services."

While in Tennessee, Parkhurst remarried and after the war attempted to practice law in Nashville. Strong sectional differences, however, forced his return to Coldwater. There he again became involved in politics and was nominated for the third district Congressional seat and the Office of State Treasurer. However, he was defeated for both offices. Later he was appointed Chief Deputy Marshall of Eastern Michigan by Andrew Johnson, and served for five months before being charged with kidnapping a postal official who was involved in a scandal. President Harrison appointed Parkhurst U.S. Minister to Belgium where he served from 1888-1889. In 1894 he was appointed by President Cleveland to be Postmaster General of Coldwater. During this time Parkhurst was on the Board of Directors of the Mansfield, Coldwater, and Lake Michigan Railroad Company and was President of the Coldwater Gas Light Company. He was also active in organizing several reunions of his Civil War regiment. Parkhurst died in Coldwater in April 1906.