Since 2013, attendance to the yearly Chicago Pride Parade has steadily remained above a million attendees. This is an increase of 2,700% more than attendance in the 1980s.
There was a steady increase in attendance at the pride parade until 2005. Then, it stagnated for about 5 years, remaining around roughly 450,000 attendees. Then, on June 1, 2011, same-sex civil unions were made legal in the state. That same year, attendance increased to around 750,000.
In 2012, Illinois Cook County State’s Attorney Anita Alvarez’s office filed a motion to declare the ban on same-sex marriage as unconstitutional. The same year, attendance increased by another 100,000.
The following year was the decisive year for same-sex marriage in Illinois. In Nov. 2013, Gov. Pat Quinn signed the Illinois gay marriage bill, legalizing marriage between same-sex couples. The bill officially went into effect on June 1, 2014.
On June 26, 2015, the US Supreme Court declared the ban on same-sex marriage as unconstitutional. Same-sex marriage was officially legal across the nation.
Since then, the Chicago Pride Parade has seen high attendance every single year. Even last year, despite heavy rains, spirits were high.
For a more in-depth look into the history of same-sex civil rights in Illinois, the Chicagoist has a nice summary. For more on the national struggle for same-sex marriage rights, visit the Georgetown Law Library.