In 1753, the Masonian Proprietors of Portsmouth, New Hampshire, granted the area now called New London as "Heidelberg".

These proprietors were led by Jonas Minot of Concord, Massachusetts, but the others were Scotch-Irish immigrants living in Londonderry, New Hampshire.

Instead they recruited settlers to build roads, mills, schools, and a church—all increasing the value of their land holdings.

The township proprietors soon began a long, systematic process of subdividing and selling their properties at great profit.

In 1807, the northern half of New London was annexed, merged with an area called "Kearsarge Gore", and then incorporated as the town of Wilmot, New Hampshire.

In the early 19th century, there were three small additions to New London, including the village of Otterville in 1817.

The Warner and the Blackwater are both tributaries of the Contoocook River, which joins the Merrimack in Penacook.

The highest point in town is Morgan Hill, approximately 1,770 feet (540 m) above sea level.