The library's roots lie in the Fort Wayne Library Association, established in 1895. This association laid the groundwork for a more structured and accessible library system. The first true public library was housed in the City Hall building, opening its doors to the public in 1895. However, as the community grew, the need for a larger, more comprehensive library became apparent.

The current main library building located at 900 Library Plaza, in downtown Fort Wayne was constructed as part of a broader expansion and modernization effort. It was designed with a focus on creating an open, welcoming environment for patrons with an architectural style that blends contemporary design elements with practical functionality. The structure features large windows to allow natural light, spacious reading areas, and specialized sections for different collections and services. The main library officially opened in its new location in 1968, with subsequent renovations and expansions enhancing its facilities.

In 2007, a major renovation and expansion project was completed, adding more space and modern amenities to meet the growing needs of the community. This project aimed to preserve the library's historical significance while updating its infrastructure and services for the 21st century.

Today, the Allen County Public Library's main library serves as a vital cultural and educational hub for Fort Wayne and the surrounding region. It offers a wide range of resources, programs, and services to support lifelong learning and community engagement.