Passage Key Views ☀️💦 . Passage Key is located at the mouth of Tampa Bay in Manatee County, south of Egmont Key. President Theodore Roosevelt established Passage Key NWR in 1905 to preserve nesting colonies of native seabirds and wading birds. In the early 1900’s Passage Key was a 60-acre mangrove island with a freshwater lake. Today, Passage Key is a low-lying sandbar that fluctuates in size, and is found often completely below water during high tide. . More than 50 species of birds have used