Ammi Young (1798-1874) was born in Lebanon, NH and moved to Vermont in 1830. Following his father as a designer, his early work included the First Congregational Church (1828) in Lebanon and dormitories at nearby Dartmouth College. Young also learned by working with Boston architect Alexander Parris whose characteristic work in granite, such as Quincy Market (1825) influenced Young's subsequent government commissions. In an 1837 competition, he won the commission for the Boston Custom House and moved to Boston to superintend its construction, which lasted until 1847.
His design of the second Vermont State House (1833-38) brought him fame and success, which eventually led him to become the first Supervising Architect of the U.S. Treasury Department in 1852. As a federal architect, he was responsible for designing numerous custom houses, post offices, courthouses and hospitals, across the United States. The buildings designed under his supervision emphasized fireproof construction and extensive use of cast iron and other metal as well as masonry. Many displayed classical revival modes while others reflected Italianate and Italian Renaissance styles.
Young’s sole Lowell design was the Middlesex County Courthouse (1850) on Gorham Street in the South Common Historic District. Built in the Romanesque Revival style, the brick structure is offset by decorative wood trim found in window hoods and arched cornice while the roof is crowned with an octagonal clock tower topped by symbolic scales of justice. The 1850 courthouse was moved to the rear of the lot in 1895 and a Neoclassical addition built along Gorham Street.