After his graduation from King's College, he studied law and was admitted to the bar of New York City in 1771. He practiced law in New York and lived across the river. During the 1830s, he developed the land around his estate into the
Elysian Fields, a popular weekend recreational and entertainment destination for New Yorkers during the 19th century. Stevens bought a farm in Dutchess County, New York from
John Armstrong Jr. Armstrong had converted a barn into a two-story Federal style dwelling with twelve rooms. Stevens made improvements to the estate, including a half-mile race track. He later sold the property to John Church Cruger (1807–1879), husband of Euphemia Van Rensselaer, daughter of
Stephen Van Rensselaer. The Crugers named the estate "Annandale". In 1776, at age 27, he was appointed a
captain in
Washington's army in the
American Revolutionary War. During the War, he was promoted to
colonel and became
Treasurer of New Jersey, serving from 1776 to 1779. In 1790, Stevens petitioned Congress for a bill that would protect American inventors. Through his efforts, his bill became a law on April 10, 1790, which introduced the patent system as law in the United States, In 1799, Stevens was named to the Board of Directors of the
Manhattan Company. As one of the original stockholders and directors of The Manhattan Company, Stevens was appointed to a three-person committee, along with John B. Coles and
Samuel Osgood, to explore the best ways to supply water to New York City. He ultimately became the company's consulting engineer and succeeded in convincing his fellow directors that steam pumping engines should be used and installed.
Steamboats In 1802, Stevens designed and a built a single screw steamboat using a rotary steam engine, a primitive single stage turbine. However, due to poor sealing, the design was abandoned and he would switch to using more conventional reciprocating engines for future steamboats. In 1804, Stevens built the
Little Juliana, a twin screwed steamboat. She was one of the first steamboats to incorporate twin screws and a high pressure steam engine. She successfully sailed down the Hudson in May 1804. In October 1811, Stevens' ship the
Juliana began operation as the first
steam-powered ferry (service was between New York City, and
Hoboken, New Jersey). The first railroad charter in the U.S. was given to Stevens and others in 1815 for the
New Jersey Railroad. The charter essentially gave Stevens and his partners, through the
Camden & Amboy Railroad, a monopoly on railroads in the state of New Jersey. In 1825, he designed and built a steam locomotive, which he operated on a circle of track at his estate in
Hoboken, New Jersey. ==Personal life==