Being mostly connected to his home in Rockland, Maine throughout his life; he also served as a state representative, militia leader and Freedmen's Bureau agent, and became a business magnate.

[1] In 1857 he was elected to the Maine House of Representatives and in the next year became Adjutant-General of the state's militia, serving on that post till the start of the American Civil War.

[4] After the American Civil War broke out Tillson resigned his posts, became an artillerist in late 1861 and organized the 2nd Maine Battery.

Throughout the winter he and his unit were kept in the state by the Trent Affair, eventually leaving and joining the Army of Virginia in April 1862.

Later in the year he was made Inspector of Artillery of the defences at Washington D.C..[4] In March 1863 he was promoted to Brigadier General, backdated to November 29, 1862.