The history of environmental law in the US can be traced back to early roots in common law doctrines, for example, the law of nuisance and the public trust doctrine. The first environmental statute was the Rivers and Harbors Act of 1899, which has been largely superseded by the Clean Water Act (CWA). However, most current major environmental statutes, such as the federal statutes listed above, were passed in the time spanning the late 1960s through the early 1980s. Prior to the passage of these statutes, most federal environmental laws were not nearly as comprehensive.