COLLINSVILLE, Ill. (AP) - A historic site in southwest Illinois is hosting an event to mark the arrival of spring.

The Illinois Historic Preservation Agency has announced that the Cahokia Mounds State Historic Site will hold a dawn event Sunday.

Visitors are invited to gather at 6:45 a.m. to see dawn break over a model of a calendar used when Cahokia Mounds was home to thousands of Native Americans.

Officials say the vernal equinox happens when the day is equally divided between the hours of darkness and light. It's technically Monday, but the site marks the day on the closest Sunday.

Cahokia Mounds is home to one of the largest Native American earthworks. It was the location of a large city of thousands of residents from the Mississippian culture, which flourished 1,000 years ago.

For more information on the equinox event, visit Illinois South Tourism.