The main village in town, where 711 people lived at the 2020 census, is defined as the Loudon census-designated place and is located along the Soucook River at the southern terminus of New Hampshire Route 129.

The town of Loudon was originally incorporated by Governor John Wentworth on January 23, 1773.

The new town was named in honor of John Campbell, 4th Earl of Loudoun, a Scottish soldier and leader of British military forces in North America during the French and Indian War.

[4] Loudoun also helped to establish an independent company of colonial militia, called Rogers' Rangers, who were attached to the British Army during the French and Indian War.

[1] The town's highest point is near its northern border, where an unnamed summit just north of the location known as Sabattus Heights reaches 1,050 feet (320 m) above sea level.

[9] Loudon is home to the New Hampshire Motor Speedway, which in the NASCAR Cup Series is home to the Ambetter 301 and formerly the ISM Connect 300, in the NASCAR Xfinity Series the ROXOR 200, formerly in the NASCAR Camping World Truck Series the UNOH 175, in the American Canadian Tour the Bond Auto Invitational, and is also home to the Loudon Classic, known as "America's Oldest Motorcycle Race".