The governor says the new law will cement Illinois as a national leader in fighting climate change, setting the state on a path to 100% clean energy by 2050.
The bill was by the Illinois Senate on Monday and aims to put the state on a path to closing coal, oil and natural gas power plants in the coming decades.
Most notably affected are municipally owned utilities in the capital city of Springfield and in Marissa, 41 miles southeast of St. Louis.
It also seeks to boost the development of wind and solar energy across the state and to put more electric vehicles on Illinois roads. Pritzker wants 1 million electric cars on roads by 2030.
Pritzker signed the legislation at the Shedd Aquarium and talked about its significance.
"With economic growth and jobs woven into its fabric, this new law is the most significant step Illinois has taken in a generation toward a reliable, renewable, affordable and clean energy future in a generation," Pritzker said.
Critics say it means record increases in electric bills.
Springfield taxpayers have upgraded City Water, Light & Power to clean up its emissions. And the 2012 opening of Marissa’s Prairie State Generating Co., under clean air laws endorsed by Democratic President Barack Obama’s administration, reveals the economic and ideological struggle over the severity of the threat of climate change and how best to halt it.
While action around the edges on clean air has continued for decades, Pritzker made the idea a campaign promise and, upon taking office in 2019, found himself among other newly elected Democratic officeholders who embraced similar plans.
The Associated Press contributed to this report.