The town was granted by the authorities of New Hampshire, to Jonathan Wiggin and others, in 1727, and was originally 9 miles (14 km) square, and covered nearly all the territory granted to Ebenezer Eastman and others, by the authorities of Massachusetts, two years previous, under the name of Pennacook (now Concord). Massachusetts claimed to hold authority over a large portion of the territory of New Hampshire for many years, till the final boundary line was established, in 1741, giving New Hampshire more territory than it had ever claimed. These complicated lines of the two towns coming from two different authorities, were not settled decisively till after the final separation of the two states. The government of New Hampshire gave Bow the preference in its grant of 1727, and did not recognize the title of the Pennacook grantees, and in the bill giving a charter for the parish of Concord, it was worded as "taking a part of the town of Bow," etc. Although Concord was granted and surveyed before Bow, its final organization was 38 years after it. Bow gained a victory over Concord in its original title; still it was obliged to yield over two-thirds of its territory to Concord, Pembroke and Hopkinton, establishing their final boundary lines at different times, from 1759 to 1765.

The town's name comes from its establishment along a bend, or "bow", in the Merrimack River. The first census, taken in 1790, reported 568 residents.

In 1874, the Concord Railroad passed along the eastern border of Bow. It is now the New England Southern Railroad.

According to the United States Census Bureau, the town has a total area of 28.4 square miles (73.6 km²), of which 28.0 sq mi (72.6 km²) is land and 0.39 sq mi (1.0 km²) is water, comprising 1.38% of the town. The highest point in Bow is Picked Hill, at 915 feet (279 m) above sea level, in the southern part of town. Nearby Wood Hill and Brown Hill also top 900 feet (270 m). Bow lies fully within the Merrimack River watershed.

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