Final answer:
The St. Louis Mounds, specifically those at Cahokia near St. Louis, represent significant historical earthworks constructed by the Mississippian culture. Although recent threats were not detailed, mounds like these generally face risks from urban development and environmental degradation. The complexity of these structures demonstrates the advanced societal organization of pre-Columbian native populations.
Step-by-step explanation:
The mounds near St. Louis, particularly in Cahokia, are historically significant earthworks constructed by native populations, most notably the Mississippian culture. The Cahokia Mounds, believed to be created by a society that lived in large cities and cultivated crops, were at the center of a large, complex settlement. These mounds served multiple purposes, including burial sites, platforms for ritual performances, and seats of power for leaders.
Recently, what threatened the St. Louis Mounds was not explicitly mentioned in the provided information, but generally, such sites can be threatened by urban development, environmental factors, erosion, or looting. The significance of these structures is highlighted by the efforts it took to build them, such as the construction of Monk's Mound, which required moving about 55 million cubic feet of earth.
The history of these mounds is intertwined with the story of native cultures in North America, particularly those of the Mississippian era, dating from around 600 CE to 1400 CE. The largest and most complex of these was Cahokia, located just across the Mississippi River from St. Louis, which served as a major hub of political and trading activities. Their construction and the advanced societal organization required to build such structures, illustrate a far more complex and settled civilization than many European explorers originally believed existed in pre-Columbian America.