The higher speeds take effect June 26 and will reduce the duration of the trip from the current five hours and 13 minutes. Trips from St. Louis to Chicago are a few minutes shorter, according to Amtrak timetables.
Existing maximum speeds on the route are 90 mph.
In addition to increasing speeds, the $1.96 billion project also provided safety improvements at 212 grade crossings, Pritzker said.
"The railway has always been a vital component of our state’s infrastructure, but today we are taking a major step in modernizing rail services," U.S. Sen. Dick Durbin said.
Funding for the project includes $1.66 billion in federal funding, primarily through an American Recovery and Reinvestment Act grant awarded that year, and $300 million in state and non-federal funds.
The project broke ground in 2010 and was completed in 2018. But it has gone through several years of test runs.