treasures in St. Louis and on the east side were lost to development. Illinois researchers discovered the remains of several earthwork mounds. In the East St. Louis area, 50 mounds had been mapped before the Civil War, and seven remain visible today. The largest is estimated to have been originally 40 feet high and would have nearly covered a football field. Around the remains of this mound, researchers have discovered evidence of burial mounds, a large plaza, a wooden defensive palisade and several other Mississippian culture structures. These indicate that it was a ritual center. The 500-acre prehistoric site is now called the East St. Louis Mound Center. The state and University of Illinois are trying to develop coordinated projects with East St. Louis and businesses to use the mounds and artifacts as attractions for heritage tourism. It was built by the Mississippian culture, which extended throughout the Ohio and Mississippi valleys. It reached its peak in this region about AD 1100–1200 at the nearby major center of Cahokia, a designated UNESCO World Heritage Site within the present-day boundaries of Collinsville. A complex urban center estimated to have had a population of perhaps 20,000, this site is about five miles from East St. Louis. In 2012, archeological work prior to construction of the Stan Musial Bridge across the Mississippi discovered artifacts and evidence of a formerly unidentified 900-year-old suburb of Cahokia in present-day East St. Louis. This site had not been mapped in the 19th century, and was unknown. The Mississippian culture site is in a present industrial wasteland. Researchers found evidence of more than 1,000 dwellings and the base of an earthen pyramidal mound. It would have been one of dozens of mounds when the community was active, based on the size of the residential population of this site. Discovery of the site led scholars to increase their estimates of the total population of the Mississippians at Cahokia and in the area, now thought to have been about 20,000. They did not have the time to excavate the entire area. It is on private land and subject to risk of destruction by development. Geography East St. Louis is located at (38.616,-90.133). According to the 2010 census, East St. Louis has a total area of , of which (or 97.36%) is land and (or 2.64%) is water. Climate East St. Louis, like all of Southern Illinois, is classified as humid