Here you go....(cut and pasted):
The Delta was originally populated by the Maidu Indians. Spanish explorers first arrived on the scene in 1772, and were followed by many others, including the trappers who introduced malaria in the early 1800's, resulting in the death of many of the Maidu people. With the discovery of gold in the California foothills, men began to flock to this new world in search of their fortune. At the same time, settlement of the Delta was commencing. These early farmers needed a way to keep their lands from flooding in the spring and winter, and thus began the construction of the levee system which defines the Delta today. A large population of Chinese had come to the area following the completion of the Transcontinental Railroad, and provided much of the labor to build the levees. The first levees were made from the peat soil of the Delta, which is great for growing crops, but not a very good building material. These early levees were prone to leak and fail, and by the late 1800's, the recently invented clamshell dredge had taken over the building of the levees. This construction lasted for about 40 years, and the maintenance continues to this day.