The primary settlement in town, where 501 people resided at the 2010 census, is defined by the U.S. Census Bureau as the Alton census-designated place (CDP) and is centered on the intersection of New Hampshire Route 11 and New Hampshire Route 140. The town also includes the village of Alton Bay, a long-time resort located beside Lake Winnipesaukee.
Originally called New Durham Gore because of rocky upland areas, or "gores," the town was settled in 1770, mainly by farmers because the highland areas provided less frost. Merchants then filled the lowlands. Early Alton history recounts stories of the merchants trying to convince the farmers to incorporate. They would succeed on 15 January 1796, when the community was named after Alton, a small market town in Hampshire, England.
Alton was part of Strafford County until Belknap County was erected on 22 December 1840. By 1840, the village of Alton existed at the town's center. In 1847, the Cochecho Railroad began bringing passengers and freight to Alton Village and Alton Bay. By 1859, the town had two gristmills, seven sawmills, and five shoe factories. But the most famous business was the Rockwell Clough Company, established by William Rockwell Clough, inventor of the corkscrew. By 1903, his company was producing 30 million corkscrews worldwide.
Since the mid-19th century, however, tourism has been the principal business. In 1863, the Adventist Campground held their first camp meeting at Alton Bay, which was the terminus of the Dover and Winnipiseogee Railroad. In 1872, the Boston & Maine Railroad launched at Alton Bay the steamer Mount Washington, the first side-wheeler and largest vessel on Lake Winnipesaukee. When destroyed by fire in 1939, a replacement ship was found, also christened Mount Washington. Today, it continues to carry summer tourists between stops on the lake. The railway survived until 1935, and the old station at Alton Bay is now a community center.