In 1919 the "Illini Union" was first launched in space that the University rented on the first floor of the YMCA, now Illini Hall. By 1927 they had taken over the entire building and spread into the Bradley Arcade building as an annex. In 1935, theUniversity of Illinois Foundation was established with one of its primary goals to fund a new building to house the Illini Union. It organized a $525,820 grant from the Public Works Administration to fund the construction and a $656,000 loan from the Connecticut Mutual Life Insurance Company, later repaid through a student fee, to pay the costs of the building itself. In June 1938 the "Advisory Committee on the Management and Operation of the Illini Union Building" was formed, which became the Illini Union Board in January 1941. In 1939 actual construction of the building got underway, one of the first to be funded with federal, rather than state funds, and on February 5, 1941 it finally opened its doors.
At 10AM Saturday morning, November 1, 1941, the Illini Union was formally dedicated on the Illini Union Terrace. The American Georgian building recalls Williamsburg , Virginia during colonial times. In fact, more than 40 volumes on colonial architecture were used its design and its interior woodwork was carved by hand whenever possible. There are five main lounges in the Union: Faculty-Alumni Lounge, Main Lounge, General Lounge, Pine Lounge, Wedgewood Lounge. The Pine Lounge is known for its elaborate wood paneling, including an ornate letter carving above the fireplace that spells "Illini", while the Wedgewood Lounge is based on the Supper Room in the Governor's Palace at Williamsburg, Virginia. There are also several other multi-purpose and dining rooms, including the Colonial Room, which offered table d'hote lunch and dinner in elegant surroundings, including Chines wallpaper and Chippendale furniture. The Browsing Room also featured elegant wood paneling with matching bookshelves holding 1,500 volumes and insets running around the perimeter of the room to hold busts of famous authors. The center of the building holds the Grand Ballroom, with its "colonial windows, heavy crimson draperies, colorful chandeliers, and highly-polished Fontainebleau floors". In the basement the two main student dining options were the Commons, which was a basic cafeteria, and the Tavern, which was open until 11PM each night and served "fountain drinks, sandwiches, and other light food".
Appreciation for tradition may be found throughout the building, but especially in the Union's two clock towers. Each of the towers is topped by a 11-foot bronze weather vane, which supports a bronze arrow 8 feet in length. The arrows are in the shape of an Indian arrowhead, with the "feathered end slit with traditional Illini cutouts indicating the 4 phases of the moon and 3 wigwams". The northern clock tower holds the fourth class gift given to the University, the class of 1878's clock. Originally installed in the bell tower of New Main University Hall, it was saved when the building was razed and installed in the Union 's clock tower. The same Union clock tower also holds the chapel bell from New Main, which once tolled students to mandatory chapel service. In a 100-year tribute to the 1878 clock, a grandfather clock rings the hours in the north lobby of the Union, a gift of the class of 1978.
The Union 's first birthday featured First Lady Eleanor Roosevelt, who cut the celebration cake. In 1962, a $6.9M addition expanded the Union significantly, adding additional guest rooms and lounge space, while also debuting the new bowling and billiards recreation centers.
The original goal of the Union was to "erect a building which would be not only a distinguished social center, open to all students, faculty, and alumni, but also to inspire those who use it with the best traditions of our early American way of life". In this pursuit it succeeded brilliantly, as Alfred Bonds proclaimed on its tenth anniversary, "I would venture to say that there has been far more philosophy of life learned over coffee or cokes at the Union than has come out of many of our philosophy classrooms".