In 1845, Schouler headed a commission that investigated mill conditions in Lowell and recommended against a proposal to shorten the work day to ten hours.

Schouler was a delegate at the 1853 Massachusetts State Constitutional Convention, where he expressed the view that corporations were merely devices for people to avoid paying debts.

In 1858, Schouler moved back to Boston and in 1860 he was appointed Adjutant General of Massachusetts.

In 1861, a Massachusetts militia training camp was named for him, but later renamed for Secretary of War Edwin Stanton.

In 1864, Schouler brought attention to Lydia Bixby, a Boston widow who lost several sons in the war; leading Abraham Lincoln to write a moving letter of condolence to her.