Tilton School was founded in 1845 as a secondary school for boys and girls when both dormitory students and day students were accepted and about 76 boys and girls formed the first student body. Two buildings, a boarding house and a classroom building were built for the School in Northfield, New Hampshire, which is just across the Winnipesaukee River from the present campus. In the 1860s, a fire burned part of the school and forced relocation across the river, to the present campus. Several brick buildings were erected, to be replaced in the 1880s by Knowles Hall.
Over the years, Tilton School has served many purposes, which were always related to the needs of the times. It has been a coeducational boarding school, a boys' boarding school, a public school, a female college, a junior college, and a secondary school with both college and general courses.
In 1939, Tilton ceased serving as the local high school and became strictly an independent boarding and day school for boys. In 1958, the "general diploma" was dropped and only college preparatory courses were offered. In 1970, Tilton once again became co-educational.
To this day, Tilton School remains coed with a total of 250 students and growing. Students from around the world makeup this wonderful community on the Hill.