While residing in Alton, Illinois, in the 1830s, he managed a number of groceries in the region, especially in St. Louis, Missouri in the antebellum period.

He was an abolitionist and on November 7, 1837, had helped defend one of his warehouses, where he had allowed publisher Elijah Parish Lovejoy to hide a printing press for the Alton Observer from an pro-slavery mob.

His father Benjamin I. Gilman graduated in the first class of the Phillips Exeter Academy, a private preparatory school.

Supporting the abolition movement, he allowed publisher Elijah Parish Lovejoy to hide a recently acquired printing press in a Gilman warehouse in Alton.

[3] Before the Civil War, Gilman moved to New York City and entered the family banking business.

They had nine surviving children together, five sons, including Arthur (1837-1909), Winthrop S., Jr. (1839–1923), Theodore (1841–1930), and Benjamin Ives Gilman (1852-1933); and four daughters.

[3] After Arthur's health declined, he retired to his estate 'Glynllyn' in the Berkshires near Lee, Massachusetts,[5] and returned to earlier literary interests.