Amos Bemis was born in Sudbury, Massachusetts, on 24 November 1762. He was married in Greenwich, Massachusetts, in January 1786, to Lydia Goodenow of Petersham. 

Amos served as a volunteer from Winchendon. His name was on a list of men raised for the six months' service and returned by Brigadier General Patterson of the Continental Brigade as having passed muster in a return dated Camp Totowa, New Jersey, on 25 October 1780. Amos was also a private in Captain Joseph Killam's Company, Colonel Rufus Putnam's 5th Regiment. He was listed on the muster roll dated West Point, New York, 10 January 1781. He enlisted for six months on 9 July 1780 and was discharged on 9 January 1781. Amos served at Fort West Point, New York, on the Hudson River, during the "Benedict Arnold" treason episode. On 26 October, a general review of the troops was given at Totowa, New Jersey, for General George Washington, several other generals, and the French Ambassador. They were all on their return from Philadelphia. Amos Bemis was among the enlisted men at Camp Totowa who were reviewed.

Amos and his wife Lydia moved to Baltimore, Windsor County, Vermont, sometime before 1794, purchasing a small portion of land from his brother, Reuben, "the southern half of Joseph Webster's right, bordering on the Chester line, of about 75 acres...." Amos built the first log cabin in the town of Baltimore and located on what was afterward called 'the Hayward lot.' The 1800 census showed Amos with a family of three boys and one girl under the age of ten years and a boy and girl between the ages of ten and sixteen. He later built a frame house a little down the hill from the cabin. Amos was active in town affairs. He was elected 'Tithingman,' 'Hayward,' and 'Highway Surveyor' of the South District several times. In 1794, he served on a committee to divide the town into school districts and was also elected to the office of town Grand Juror. Baltimore was set off as a separate town from Cavendish in 1793, mainly because of the barrier of Hawk's Mountain. A fire in Baltimore in the early 1830s caused many of the town's records to be lost forever.

Amos applied for a survivor's pension (W23589) for his Revolutionary war service on 7 August 1832 when he was 69 years old and living on his farm in Baltimore. He related in his affidavit that in about 1797, he moved to Chester, Vermont, where he lived for two years before settling in Baltimore. After his death, Widow Lydia applied for her widow's pension at the age of 85 on 25 May 1846. Her daughter, Nancy Horton (aged 52 in 1846), stated in a supporting affidavit that her father and mother had nine children, of which four were older than she was. The youngest child was Lewis Bemis, who was aged 38 in 1846. Her father's brother, Abel Bemis, was aged 74 in 1846 and living in Winchendon, Massachusetts. Amos died in Baltimore on 31 October 1835 at age 73.