A bill to make Cahokia Mounds part of a new national park was introduced in Congress on Thursday by Republican Rep. Mike Bost.

The Cahokia Mounds and Mississippian Culture National Historic Park would include Cahokia Mounds, plus ancient mounds in St. Clair, Monroe and Madison counties in Illinois — and Sugarloaf Mound in St. Louis, the last remaining mound in the city.

The National Park Service and state and local agencies would manage the park.

“We’re hoping that the Senate will move on this, as well, and then we can get it to the president’s desk,” said Bost, of Murphysboro. “So many other national treasures have been put into the Park Service, and this is a place where it should naturally be.”

The bill is co-sponsored by Missouri Rep. Lacy Clay, D-University City, and Illinois Reps. John Shimkus, R-Collinsville, and Rodney Davis, R-Taylorville. The proposed park includes sites within their districts.

U.S. Sen. Dick Durbin, an Illinois Democrat who grew up in Southern Illinois, also backs efforts to give national park status to the mounds, Bost said.

“So, you know that it’s not going to stop just here in the House,’’ Bost said. “Senator Durbin is well aware of this and taking an interest in it.”

Even with bipartisan support, the process will take time, Bost said.

“An act of Congress doesn’t move very quickly, but we’re going to sure try to move it as quick as we can,’’ he said.

Cahokia Mounds, a 2,200-acre state historic site in Collinsville, protects more than 70 mounds built by the Mississippians 1,000 years ago. It was “America’s First City’’ — a hub of mounds where the ancients lived, worked and worshipped atop earthen structures.

The Mississippians built “satellite” mounds across the region, stretching west across the Mississippi River. At its peak in 1200 A.D., an estimated 100,000 people lived at Cahokia. Researchers say the site was abandoned by 1300 A.D., but they aren’t sure why.

Support for the effort has always been bipartisan, said Ed Weilbacher, vice president of Heartlands Conservancy, which has led the national park effort.

His staff worked on the bill with Bost’s staff and other area members of Congress.

In a recent interview, Weilbacher said it was important to include sites beyond Cahokia Mounds in the measure because the Mississippians built mounds across the region. Development has destroyed hundreds of the earthen structures, including most of the mounds in St. Louis, which was once known as “Mound City.”

“As a group here in Illinois, we have not let the river divide us,” Weilbacher said. “We have looked at it as a culture that was in the Midwest, and we have to think about it at that period of time. We had no states when this civilization existed in the Midwest.”

A site can enter the National Park Service in two ways: Most are established by an act of Congress, signed by the president into law. Or, the president can invoke the Antiquities Act and designate areas as national monuments. National parks and national monuments are equal in status.

Weilbacher's group had hoped that President Barack Obama would declare Cahokia Mounds a national monument before leaving office in January 2017. When that didn’t happen, Heartlands refocused on the congressional route.

An important component of the proposed national park is that it would create a collaborative partnership between the National Park Service and local and state governments, Bost said.

Illinois would retain ownership of Cahokia Mounds.

A study published by Heartlands in 2014 concluded that such a partnership between the National Park Service and the state of Illinois would be both beneficial and feasible. “The Mounds — America’s First Cities” included input from local residents, archaeologists and Native American groups.

The report noted the importance of the mounds to Native American tribes and nations that consider them sacred.

The Osage Nation, which owns Sugarloaf Mound in St. Louis, has supported the effort, Weilbacher said.

Last year, nearly 300,000 people from 80 countries visited Cahokia Mounds.

In 1982, the United Nations Educational, Scientific and Cultural Organization recognized the cultural and archaeological significance of Cahokia Mounds and named it a World Heritage site. It is also a U.S. National Historic Landmark and is on the National Register of Historic Places.

The St. Clair County Board recently voted unanimously to back the initiative. Heartlands has also received letters of support from the city of Collinsville and the East-West Gateway Council of Governments.

In May, the Illinois House of Representatives passed a resolution, sponsored by Rep. Jay Hoffman, D-Swansea, in support of a national park. The Legislature had previously supported the plan to make Cahokia Mounds a national monument.

In 2018, the Illinois Department of Natural Resources signed on to the national parks plan. The department took over administration of Cahokia Mounds in 2017 after then-Gov. Bruce Rauner dissolved the Illinois Historic Preservation Agency, which had overseen the site.

Follow Mary Delach Leonard on Twitter: @marydleonard