After graduating from Columbia, he studied law and was admitted to the bar and built up a lucrative practice. In 1814, during the War of 1812, he was appointed Assistant Judge Advocate General of the U.S. Army.[2]
New York County District Attorney
From 1817 to 1818 and again from 1821 to 1829, he was New York County District Attorney.[3] On September 15, 1826, Jacob Barker, Henry Eckford, and other leaders of Tammany Hall were indicted for allegedly committing millions of dollars in acts of fraud against banks, insurance companies, and private citizens, and Maxwell subsequently prosecuted them for "conspiracy to defraud."[4] The first trial ended in a hung jury in October 1826, although some defendants were convicted in a second trial. Eckford, a famous shipbuilder and entrepreneur of the time, was not prosecuted again after the first trial and sought an apology and public statement of his innocence from Maxwell, but succeeded only in getting Maxwell to make a statement that Eckford had been duped by others into illegal acts. Eckford challenged Maxwell to a duel in December 1827, but Maxwell ignored him.[5]
Collector of the Port of New York
After his term as New York County District Attorney ended in 1829, he resumed his law practice for the next twenty years, occupying a prominent position in the New York bar,[6] along with his law partner, Ogden Hoffman.[7]
Maxwell was married to Agnes Stevenson (1796–1866), with whom he had four children:[6] Hugh Maxwell, John Stevenson Maxwell (1847–1918), Ann Eliza Maxwell, and Agnes Maxwell.[6]
He was a member of the New-York Historical Society and was elected a member of Saint Andrew's Society of the State of New York in 1811, serving as manager from 1826 to 1828, second vice-president from 1828 to 1832, first vice-president from 1832 to 1835, and as President from 1835 to 1837.[6] He was known for his love of classic literature and he entertained friends, including Thurlow Weed, William C. Rhinelander (grandfather of T.J. Oakley Rhinelander) and James Lenox, at his library, considered one of the best private collections in New York.[6]
Maxwell died on March 31, 1873, at his residence, 14 St. Marks Place in New York City. He was buried at
Oak Hill Cemetery in Nyack, New York.[9]