Regarded as the primary artist of the final decades of Western exploration, Thomas Moran made eight trips West between 1871 and 1892 and created a body of oil and watercolor sketches that remain a primary record of that period. In fact, his painting was so associated with the West that he was referred to as T. Yellowstone Moran. In 1873, he began signing his name with a monogram that incorporated "Y" into his initials, and from 1911, he added a thumbprint.

He was born in Bolton, Lancashire, England, and his father was a hand-loom weaver. In 1844, his family emigrated to Philadelphia where in 1853, he apprenticed to a wood engraving firm and sketched designs on blocks. He also studied with his old...