In 1815, he moved to Boston, where he found a position in the office of Charles Bulfinch. Like his famous employer, Parris produced refined residences, churches and commercial buildings. When in 1817 Bulfinch was called to Washington to work on the U.S. Capitol Building, Parris helped complete the Bulfinch Building home of the Ether Dome at Massachusetts General Hospital. With Bulfinch's departure, Parris soon became the city's leading architect, and a proponent of what would be called "Boston Granite Style," with austere, monolithic stonework. Around 1818-1823 he kept an office on Court Street. He belonged to the Massachusetts Charitable Mechanic Association.