[4] The first mention of the territory containing the current town of Merrimack among written records was the petition of Passaconaway to the General Court of Massachusetts for a grant of land to include a part of this region.

This was in 1662, and in the autumn of that year the court acceded to the request, and the aged sachem and his associates were granted a strip of country a mile and a half wide on both banks of the Merrimack at this section of the river.

Although the boundaries of this grant are not specifically known today, it is probable that the chieftain held at least a portion of the current town of Merrimack.

On June 25, 1734, Massachusetts granted the town organization as "Naticook", which was made up of Litchfield and part of Merrimack.

[5] On April 2, 1746, Governor Benning Wentworth signed a charter establishing that the land from Pennichuck Brook to the Souhegan River became the Town of Merrymac.

Turkey Hill on Meetinghouse Road is the first mentioned in the town records, but Thornton Cemetery on Route 3 has the oldest gravestone.

[2] The highest point in Merrimack is an unnamed hill in the northwestern part of town that reaches 512 feet (156 m) above sea level.

However, the boundaries and exact definitions are unclear due to the expansion of suburban development in the town during the latter half of the 20th century.

The area of town near Naticook Lake and Continental Boulevard, its name comes from Matthew Thornton, one of the signers of the Declaration of Independence who lived in Merrimack and is now buried in a cemetery near the intersection of Daniel Webster Highway (U.S. Route 3) and Greeley Street.

The northern portion of the town, Reeds Ferry is centered on the current intersection of Bedford Road and Daniel Webster Highway.

The boundaries of the area are unclear, as the northwestern part of town near Baboosic Lake is not traditionally considered a portion of Reeds Ferry.

While as a defined village it was located mostly near the Merrimack River, the area near Baboosic Lake may now possibly be seen as part of Reeds Ferry.

However, the southeastern portion of town near Harris Pond might also be considered part of South Merrimack or Thornton's Ferry.

Largely considered to be located at the Public Library on the corner of Baboosic Lake Road and Daniel Webster Highway, Merrimack Village was built along the Souhegan River that roughly cuts the current town in half.

Opened in 2012, the Merrimack Premium Outlets are a 560,000-square-foot (52,000 m2) retail mall area with 12 buildings, parking lots, and other site improvements located off exit 10 of the Everett Turnpike.

[citation needed] The Rock'N Ribfest, hosted by the Nashua West Rotary Club, was an annual event held from 2003 through 2018, the proceeds of which benefited many local charities.

In 2019 the event was hosted by the Merrimack Rotary Club and renamed the Great American Ribfest and Food Truck Festival.

[19] The ribfest is held on the Anheuser-Busch grounds in Merrimack and features BBQ, children's games and activities, music, and other entertainment.

As a large, suburban community located directly between the state's two largest cities (Manchester and Nashua), Merrimack plays a disproportionate role to its size every four years in the New Hampshire primary; in almost every Fourth of July preceding a presidential election, every presidential candidate will march or have a float in the town's Fourth of July parade.

In 2020, Joe Biden was the first Democrat to carry the town with a majority of votes since Lyndon B. Johnson's landslide victory in 1964.