San Manuel is known to be a forest covered with thick marshes and grasses during the earliest times. It is also covered with dense marshlands, lakes and creeks. Wild animals gamely roamed into the woods and wilderness until the adventurous people from Zambales and Pangasinan discovered the fertile grounds of the area. Later, migrants from the Ilocos region settled into the lush green fields of the place and started new life. The settlers cleared the lands using their crude implements and started growing rice and corn. The early settlers also engaged in hunting wild deer, pigs, birds and other forest animals to sustain their subsistence.
The town of San Manuel was the biggest village of Moncada and was called San Jose in 1902. In 1909, it was converted as a town, and was name in memory of its founder, Don Manuel de Leon.
When the prosperous village of San Jose was separated from the town of Moncada, the jubilant and proud people of the town grouped themselves together to intensify the progress and development of the municipality.
The municipality of San Manuel is bounded on the north by the province of Pangasinan, the province of Nueva Ecija on the east, municipality of Anao, Tarlac on the south and the town of Moncada, Tarlac on the southwest. It has a population of 22,747 (NSO, 2005) and its economy is totally dependent on agriculture.
San Manuel as a border town is gradually booming with economy. Its robust agriculture generates agro-industrial enterprises that largely sustain its economy. Small business and industrial establishments begin to show and grow. This indicates boom and confidence. San Manuel has a young economy, yet, it is surging high and beyond.