In 1816, Tillinghast was admitted to the Rhode Island bar and opened his first office, in the village of Chepachet.
In 1843, Tillinghast represented Providence for a single term in the Rhode Island General Assembly.
Between 1913 and 1916, later famous civil liberties advocate Zechariah Chafee practiced for Tillinghast & Collins.
In 2000, it merged with the Boston firm of Perkins Smith & Cohen and called its Rhode Island office Tillinghast Licht Perkins Smith & Cohen, but the firms split only a few years later, and Tillinghast Licht returned to its former name.
In May 2008, Tillinghast Licht announced that it will wind down business in the next few months, with six key lawyers joining Adler Pollock & Sheehan.