Seneca, which competed with Thedford for the county seat, was established in January of 1888 and was for several years the largest town in Thomas County.
The town was the site of a railroad depot, yard, and roundhouse.
The location of these railroad operations in the town brought Seneca a period of < prosperity until the railroad pulled out of the town in the 1922.
Seneca's peak population was in 1920 with 476 residents. During its more prosperous times, Seneca contained a lumber/implement dealership, hotels, banks, an automobile dealership, stores and services of various types, schools, churches and a post office.
Harry Truman made a whistle stop in Seneca in during
his campaign in 1948.