Yes, the area that is now New Orleans was originally a swamp. The city is located on a bend in the Mississippi River, which made the land low-lying and prone to flooding. The soil in the area is also composed mostly of marsh clay, which made it difficult to build on.
The early European settlers in the area struggled to drain the swamps and make the land suitable for development. They built a system of levees and canals to try to control the flooding, but these efforts were often unsuccessful. It wasn't until the late 19th and early 20th centuries that the city was able to build an effective system of levees and pumps to control the flooding.
Despite the challenges posed by the swampy terrain, the area was still settled because of its strategic location at the mouth of the Mississippi River, which made it an important port for trade and commerce. Today, New Orleans is a thriving city with a rich culture and history, but the city continues to struggle with flooding and the effects of sea level rise.
New Orleans was drained for building by creating a system of levees and canals. The levees were constructed along the Mississippi River and Lake Pontchartrain to hold back water during floods. Canals were also built to divert water away from the city and into nearby lakes and bayous.
In the 19th century, the city also began a process of "subsidence", which involved pumping water out of the marshy soil to make it solid enough for building. Steam-powered pumps were used to remove water from the soil, which caused the land to sink, making it even lower than sea level. This process made it possible to build on the otherwise marshy land.
In the early 20th century, the city also developed an extensive system of drainage canals and pumps to control flooding and protect the city from storm surges. The canals and pumps are controlled by the Orleans Levee District, an independent public agency, which operates and maintains the system.
Additionally, the Mississippi River Gulf Outlet (MRGO) was built in the 1960s, it was intended to shorten the shipping route from the Gulf of Mexico to the port of New Orleans, but it ultimately proved to be a major contributor to the flooding during Hurricane Katrina in 2005. It was closed and filled with sediment in 2009.
Despite these efforts, New Orleans continues to struggle with flooding and the effects of sea level rise. The city remains below sea level and is vulnerable to flooding from heavy rain, hurricanes, and storm surges.