It's a big day in Illinois; recreational marijuana has officially been legalized. Governor J.B. Pritzker delivered on his campaign promise by signing off on the measure on Tuesday. With that, Illinois became just the 11th state to legalize marijuana.

Under, the new rules, Illinois residents can purchase and possess up to 1 ounce (30 grams) of marijuana at a time. Non-residents can have 15 grams.

While many expect the new measure will have a huge impact on the state's economy, there's one other thing that could happen; a lot of people facing criminal charges could have them wiped out.

According to the Associated Press, "nearly 800,000 people with criminal records for purchasing or possessing 30 grams of marijuana or less may have those records expunged." It comes as part of a provision that lawmakers and groups demanded during the drafting process.

That won't happen immediately though. According to the AP's report, possession will remain a crime until the bill takes effect on January 1, 2020.