Mercer Beasley was an eminent New Jersey jurist. He was born March 27, 1815, in Philadelphia, Pennsylvania, to Frederick and Maria Beasley. He studied at the College of New Jersey (now Princeton) but only for a year, after which he studied the law. He was admitted to the bar in 1838 and established a successful legal practice in Trenton, New Jersey. He became active in local politics, first as a Whig and later as a Democrat, before pursuing a career in the judicial system.
On March 8, 1864, the governor appointed Beasley to a seven-year term as the New Jersey high court's chief justice. Four succeeding governors retained him, allowing Beasley to serve on the bench for almost 33 years. He gained prominence for his equitable decisions, particularly those concerning political dissent.
Beasley died from pneumonia on February 19, 1897, in Trenton.