Amasa E. Dana was born around 1839 in New York to Alvin and Diantha Dana. His father was a cabinet maker who owned $2,400 of real estate and $300 of personal property by 1860. The family moved to Bonus, Illinois, in the 1840s and then to Cherry Valley, Illinois, in the 1850s. By 1860, he was working as a manufacturer, and he owned $660 of personal property.
He received a commission as a 2nd lieutenant in the 8th Illinois Cavalry. According to his service records, he was 5 feet, 8 inches tall, with light hair and blue eyes. The regiment took part in the Battle of Antietam, the Battle of Fredericksburg, and the Battle of Gettysburg. He was promoted to 1st lieutenant in December 1862. Then, in the summer of 1864, he was promoted to captain and assistant adjutant general. He served in the Middle Military Division. He was promoted to major in November 1864, and he mustered out on May 25, 1865.
He married Anna E. Peats on December 15, 1864, and their son Frank was born around 1874. They moved to Kansas City, Missouri, after the war, and he worked as a lumber merchant. He joined the Grand Army of the Republic, and he took part in a procession in May 1882. He died sometime after 1888.