1. On July 11, 1839, the first state geological survey was completed in Illinois. Led by the famous geologist and naturalist, Dr. Leo Lesquereux, the survey documented the state's geology, mineral resources, and topography, and provided a foundation for further scientific research.

2. Another notable event in Illinois history that occurred on July 11 was the dedication of the Illinois State Capitol building in Springfield in 1888. The building, designed in the French Renaissance style by architect Alfred Piquenard, remains an iconic landmark of the state and houses the offices of the Governor, Lieutenant Governor, and other state officials.

3. In 1899, the 8th International Convention of the Epworth League, a youth organization of the Methodist Episcopal Church, was held in Chicago on July 11. Thousands of young people from across the U.S. and other countries attended the convention, which focused on spiritual development, social issues, and practical skills.

4. July 11, 1933, saw the opening of the World's Fair Century of Progress in Chicago, which ran until October of that year. The fair showcased the latest technological innovations, entertainment, and cultural exhibits, and attracted millions of visitors from around the world, making it one of the most successful fairs of the 20th century.

5. Finally, on July 11, 2018, Illinois became the 37th state to ratify the proposed Equal Rights Amendment (ERA) to the U.S Constitution, which aims to guarantee equal legal rights for all citizens regardless of sex. Although the ERA was originally introduced in Congress in 1923, it has yet to be fully ratified by the required number of states, and its status remains a contentious issue in American politics.