This article makes the case for expanded state and local protection of vulnerable streams and wetlands. Vulnerable streams and wetlands include the very smallest streams and wetlands that do not have a permanent surface water connection to larger waterbodies, yet are still vital parts of the ecosystem. The exact extent of these resources across the nation is unknown. Some preliminary estimates find that, in the contiguous U.S., headwater streams comprise 53% to 59% of the stream network, while 20% to 30% of wetlands could be considered isolated, making them vulnerable to direct impacts. Headwater streams and isolated wetlands provide a host of benefits that are just beginning to be documented, including: ecological linkages to downstream receiving waters; capacity to store floodwaters and recharge groundwater supplies; removal of excess nutrients and sediment; and exceptional biodiversity, supporting habitat for many threatened or endangered species. The primary federal authority protecting streams and wetlands is the Clean Water Act. Recent Supreme Court decisions such as SWANCC and Rapanos have potentially restricted the scope of the Clean Water Act, making headwater streams and isolated wetlands vulnerable.