After several years on the Mississippi, he and a friend left for the West Indies, but finding life there not to his liking, he returned to the United States, again making his home in Rochester.

Initially a Democrat, by 1844 he had allied with a "Democratic-Republican" faction calling for strict construction of the Constitution, and opposing annexation of foreign territory and extension of slavery.

Following a devastating fire which destroyed his Rochester home, he moved his family to Oswego in 1847, where he first worked as representative of the Troy, New York, transportation firm, Ide & Colt.

Howard, a sidewheeler steam tug, which was reportedly the first steam-powered tugboat to be constructed west of the Hudson River, the first to do business in Oswego harbor, and the first to operate on the Great Lakes.

By 1860, he was active in the Republican Party, in Oswego's Presbyterian Church, and in his work as a boatbuilder and commission merchant, shipping goods on the Great Lakes and on the inland canals to Troy and Albany.

Mattoon converted the schooner Ellsworth to a screw steamer in his Oswego boatworks, and embarked on a voyage across the Erie Canal, through a number of inland passages to Cape Fear, North Carolina, then down the Atlantic coast to Key West.

Although the Florida venture proved a costly failure, business contacts made during the voyage south led Mattoon to transport grain along the coast of Virginia and North Carolina during the winter of 1872-73.

The Ellsworth burned off Stoney Island in Lake Ontario in 1877, but Mattoon salvaged the engine and gear and installed them in his new steam barge Thompson Kingsford, which launched in 1880.

A longtime sportsman and early proponent of conservation, he served as president of Oswego's Leatherstocking Club, and was instrumental in the foundation of the National Association for the Protection of Fish and Game.

He was a guest of Captain Alexander Cuthbert aboard the Atlanta during her two controversial and ultimately unsuccessful Cup races against the American iron-hulled sloop Mischief, one off Manhattan and the other off Staten Island.

He was appointed Customs Collector for Oswego in 1883, and by 1889 served as Deputy United States Marshal for the Northern District of New York, a position chiefly concerned with marine damage claims and salvage cases.

In December 1891, Mattoon again attracted the attention of the national press with his testimony in the controversial Laura V. Appleton vs. New York Life Insurance Company suit.

He described the latter's increasingly erratic behavior as early as the 1860s and 1870s, evidenced by his claimed communication with spirits, including those of Italian unifier Giuseppe Garibaldi and the murdered "cigar girl," Mary Rogers, whose unsolved case remained a matter of much speculation, and even had even inspired a short story by Edgar Allan Poe.