John M. Thayer was born in Bellingham, Norfolk County, Massachusetts on January 24, 1820. Mr. Thayer attended rural schools and later studied law at Brown University. Arriving in Nebraska in 1854, he quickly affiliated himself with the Republican Party and thereafter actively participated in politics. Thayer served as delegate to the Convention which organized the Republican Party in the Nebraska Territory and was elected to the Nebraska Territorial Legislature in 1860-61. Then the future governor resigned to become a colonel in the First Nebraska Infantry. He commanded a brigade in the battles of Fort Donelson and Shiloh. Promoted to brigadier-general in 1862 he led a brigade during the Siege of Vicksburg. After theAmerican Civil War he was elected as one of the first two United States senators from Nebraska and served in the Senate until 1871. President Grant appointed Thayer Governor of the Territory of Wyoming in February 1875 and he took the oath of office March 1, 1875. His service ended on May 29, 1878 and he returned to Nebraska to resumed his law practice.

Thayer served two full terms as Governor of Nebraska (1887 - 1891) and part of a third term, (May 5, 1891 - February 8, 1892). He contested the results of the 1890 election, in which he lost to James E. Boyd; Boyd was initially installed as Governor, but Thayer again became Governor until the election was ruled in favor of Boyd. He then retired from public life to follow literary pursuits. John M. Thayer died March 19, 1906 in Lincoln, Nebraska.