The present library began with an offer by Amos K. Ayer, of Delavan. In cooperation with his brother, Joseph E. Ayer, they pledged to give the library $200 per year, for ten years, for the purchase of books, provided the township would appropriate funds to maintain a library.
In 1907, the Delavan Township took advantage of a recently enacted state law and voted a one and one-tenth mill tax to support a library in the spring election. This gave Delavan the honor of becoming the first tax supported library in Illinois. The library was named for Mr. Ayer, who had been active in its organization and had purchased the books and equipment of the Library of the Blue Button Army, presenting those to the township library. When formally opened in September 1907, the library had over 2000 books and was housed above the old bank building located on the corner of Locust and Third Streets.
In 1914, a grant of $10,000 was received from the Carnegie Foundation for the building and furnishing of a modern building. The present building was designed by Bloomington architect, A. T. Simmons, and is located on the southeast corner of Second and Locust Streets. It was erected on the former site of Phillips Hall which was donated by James Warren Crabb. Local contractor Ray Lillibridge was instrumental in the construction of the building.
A rental department was established in 1948, making recent books more readily available to a greater number of patrons. In 1957, the Delavan Women's Club redecorated a basement room for their meetings. For a time, the Delavan Junior Women's Club also met there. In 1983, this room was refurbished with funds from the Helen McKinstry Estate. The basement currently houses the juvenille collection and has reading and study areas available.
In 1992, the library's service area was expanded when the library was reorganized as a district, and became Ayer Public Library District. On November 12, 1998, through the rigorous efforts of past board members Glenn Allen and James Sullivan, the Ayer Public Library District was placed of the National Register of Historic Places.
November 2014 marked the 100th anniversary of the library building.
Today the library strives to meet the challenges of providing new materials, along with ever changing technology to best serve the public.