John Sanderson was born in Sunderland, Bennington County, Vermont, to John H. and Sarah (Laurence) Sanderson.[1] He graduated from Amherst College in 1839. Before the civil war erupted, he was a lawyer, secessionist Democrat and was part of the Planter Class in Jacksonville, Florida.[citation needed]
He became a member of the Florida State House of Representatives in 1843, was the solicitor of the Eastern Circuit of Florida from 1848 to 1852 and became a Florida State Senator in 1848. He was a delegate to both the Florida Secession Convention of 1861 and then to the Confederate Provisional Congress from February 5–17, 1862, replacing George Taliaferro Ward.[2]
John was married twice. He first married Mary E. Harrison (daughter of Robert Harrison of Amelia Island, Florida) on February 23, 1843. They had no children. Following her death on April 27, 1857, he later married her sister Marion R. Harrison on July 28, 1858. They had 2 children.[1]