Triangle was formed in the fall of 1906 by sixteen Civil Engineering juniors at the University of Illinois. It was formally incorporating on 15 April 1907. The date of incorporation has been designated as Founders' Day, and Triangle celebrates it every year at each chapter. Triangle's mission statement reads, "The purpose of Triangle shall be to maintain a fraternity of engineers, architects and scientists. It shall carry out its purpose by establishing chapters that develop balanced men who cultivate high moral character, foster lifelong friendships, and live their lives with integrity."