as evidenced by the many small museums that can be found in almost any Delta town. Thanks to sacdelta.com for this quick history lesson:

John Sutter was one of the first white men to navigate the Delta, in 1839. Landing at the site of the future Sacramento, he built Sutter’s Fort, which you may recall was to become the site of the beginning of the California Gold Rush, in 1848. Meanwhile John Brannan established a store near the waterfront, which later became the city of Sacramento.

Development began around 1850, and by 1869 Sherman and Twitchell Islands were protected by levees. By the end of WWI, over 1,000 miles of levees were pretty much completed, protecting over 738,000 acres and hundreds of miles of waterways.