The town's name originated from early settlers' founder, Don Manuel Sequig amid the town's existence in 1614, when Poblacion was in Pau (now Curibetbet) with a population of 2,023.
In 1688 the Convento was erected and in 1720, both the church and convent were in place at Pau but were burned down due to a bad omen superstition, hence Asingan fused San Manuel was but natives moved Guiset, a name of San Manuel (great bamboo thickets). In 1860, San Manuel was decreed a town for the second time.
San Manuel became a town, 44 years before Asingan was, but was absorbed by the latter from 1903 to 1907. (Source:Mr. Crispo Baclit, "Ti Ababa Nga Pakasaritaan Ti Ili a San Manuel, Pangasinan")
The town was named after Don Manuel Sequig, the founder and leader of the settler who explore the virgin forest from the bank of the Agno River, towards the grassy lands of the west, to the foot of the Cordillera Mountains in the North. When San Manuel became a town in 1614, the site of the Poblacion was in Pau (now known as Curibetbet) and had a population of 2,123. As the population continued to swell in 1688, the inhabitants thought of erecting the first church and convent. It was alsothe same year that Asingan was lying out its town site call sinapog. In 1720, the church and convent built in Pau were burned down and the people believed it to be a bad omen so they abandoned the site and went to Sinapog to live. This was then the time when San Manuel was absorb by Asingan for the first time. However, some of the inhabitants moved westward to the placed called Guiset, a name given to San Manuel which was derived from the great bamboo thickets that were plentiful in the area during the time. In 1860, San Manuel separated from Asingan and became a town for the second time, but its site was no longer Pau in its present location. For brief period from 1903 to 1907, due to lack of funds, San Manuel was again absorb by Asingan for the second time. San Manuel was again become a town.
Now San Manuel was known of its man-made structure, San Roque Multi-Purpose Dam Project or the San Roque Power Corporation which was the second largest Dam in Asia.