The levees were erected to safeguard public infrastructure such as roadways and pipelines while preventing floods and allowing agriculture of the rich soil. The Mississippi River has eroded its way through the city over time, leaving behind a series of hills called "river bluffs." The river bluffs serve as natural barriers against floodwaters entering downtown St. Louis from the north and west. Without the levees, these floodwaters would destroy anything in their path. The federal government authorized the construction of the initial levee system in 1872 after several major floods damaged or destroyed much of the city. The Army Corps of Engineers built the first set of levees near where the Mississippi River enters St. Louis. These original levees were made of earth and timber and were intended only to prevent floods into downtown St. Louis. They did not extend all the way up to the river bluffs like today's levees do. Over the years, the Army Corps of Engineers has continued to build new sets of levees to protect other areas of St. Louis from flooding. In fact, the current system of more than 20 miles of levees was completed in 1994. Before that time, the only protection for people living in south St. Louis County was the Municipal Service District (MSD) system.