Mercer was born 16 January 1726 at Pitsligo manse, Aberdeenshire, Scotland, to Ann Monro and the Reverend William Mercer, a minister in the Church of Scotland. At 15, he began studying medicine at the

Before the New York City Campaign, Washington had ordered two forts built to repel the Royal Navy. On the New York side of the Hudson River, Fort Washington was constructed, and Mercer

In the 2000 television film The Crossing, a dramatization of Washington's crossing of the Delaware and the battle of Trenton, Mercer is played by Roger Rees.

• Fort Mercer, located in Red Bank Battlefield of what is now the Borough of National Park, New Jersey, which was named in his honor.
• Mercer County, New Jersey where Trenton and Princeton are located, was named after Hugh Mercer.

In 1755, when General Edward Braddock's army was cut down by the French and Indians during the first British attempt to take Fort Duquesne, Mercer was shocked by the same butchery he remembered at Culloden. He came to the aid of the wounded and eventually

Succeeding generations of Mercer's family have distinguished themselves. Famous direct descendants of Hugh Mercer were his grandson Virginia governor John Mercer Patton, his sons Confederate Lt. Col Waller T. Patton and Col. George Smith Patton,

In the Broadway musical Hamilton, General Mercer is referenced by Aaron Burr in the song "The Room Where It Happens": "Did ya hear the news about good old General Mercer? You know Clermont Street? They renamed it after him. The Mercer legacy is secure."