John was born in Queensbury, Warren County, New York, and moved in the mid-1830s to Michigan, settling in Brighton, Livingston County. He was among the original purchasers of land in Brighton Township in September 1838. He is sometimes listed as Gayley Spencer in Livingston County records. John was an officer in Brighton Lodge No. 42, Masons, when it was chartered on 9 January 1851. He was one of the firs trustees of Methodist Episcopal Church of Brighton, formally organized in 1854. John married his wife, Lucy, apparently between 1850 (he is living alone at the time of the 1850 Census) and 1856 (when his wife is found in records as Mrs. Lucy Spencer).⁶

He enlisted in Company G, 11th Michigan Cavalry, on 25 November 1863, for three years. His age is listed as 40 in Civil War records but he was believed to actually be 63 when he enlisted. He was mustered in as a private on 3 December 1863. His company left Kalamazoo on 17 December, 1863 in a blinding snow storm, and arrived in Lexington, Kentucky on 22 December. On 1 January 1964, his regiment had only green wood to burn, and with the thermometer at eight degrees below zero, many of the men went to bed to keep from freezing. The regiment was armed, equipped, mounted and drilled until April 1864, when it was sent to Louisa, Kentucky. Details of John Spencer’s death on either 11 or 12 January 1864 have not been found, but could be attributed to either the harsh conditions or possibly in action during one of his company’s few skirmishes with Confederate troops during that period. Civil War records indicate he was buried in Lexington, Kentucky, but he was apparently re-interred in Brighton Village Cemetery where both old and new headstones mark his grave.^{4, 7}