In 1850 , Congress passed the Arkansas or Swampland Act , which allowed for the transfer of title for wetlands to private owners on the conditions that the land would be reclaimed . In California , more than of wetlands were partitioned under the Swampland Act , of which were in the Sacramento-San Joaquin Delta , roughly the same amount of land that has been developed to date . Agricultural interests in the Delta were protected by the building of levees , a colossal effort first undertaken by Chinese laborers from the 1850s to the 1870s . The Board of Reclamation , formed in 1861 , collectivized levee construction in the Delta by grouping islands into areas known as '' reclamation districts '' . The early levees were built of peat , and were highly susceptible to wind and water erosion . The Great Flood of 1862 obliterated much of the existing Delta infrastructure , forcing landowners to rebuild their levees higher and stronger ; more flooding in 1878 and 1881 reinforced these notions . Although land holdings in the Delta were initially limited to per buyer , this limit was repealed in 1868 , allowing large agricultural conglomerates to take entire islands and carry out massive reclamation projects . From 1868 – 1869 , the entirety of Sherman Island , some , was diked and drained by a system of levees , flumes and floodgates . By the 1890s , the original levee system had been largely replaced with stronger embankments consisting of clay dredged from nearby river bottoms . By 1900 , about , or nearly half of the Delta 's land area , had been reclaimed . Most of the farmable land in the Delta had been reclaimed by the 1920s
Great Flood of 1862
Great Flood of 1862
Sacramento–San Joaquin River Delta