Shepard Mount began studying art while apprenticed to the New Haven coach maker, James Brewster. In 1826 he moved to New York to join his brothers Henry Smith and William Sidney. In 1829, after studying at the National Academy's antique school, Mount began exhibiting his paintings at its annual exhibitions. During the following years he worked in a variety of genres but found his greatest proficiency as a portrait painter. In 1837, after establishing a promising reputation, Mount married Elizabeth Hempstead Elliott, sister of the renowned portraitist Charles Loring Elliott.
In 1841 Mount and his wife returned to Long Island and settled in Stony Brook. During the following years he received commissions to paint portraits of many of Long Island's leading citizens. Although he found financial regard as a portraitist, Mount continued to paint game pieces, genre scenes, and landscapes throughout his life, and his works were frequently included in the Academy's annual exhibitions. Mount's success as an artist has largely been overshadowed by the career of his brother William, yet during his life he enjoyed a healthy reputation as an artist.