Definitions of gulf coast on the Web:

a seashore of the Gulf of Mexico
wordnetweb.princeton.edu/perl/webwn
The Gulf Coast of the United States, sometimes referred to as the Gulf South or South Coast, comprises the coasts of American states that are on the Gulf of Mexico. These states are Texas, Louisiana, Mississippi, Alabama, and Florida and are known as the Gulf States. ...
en.wikipedia.org/wiki/Gulf_coast
Gulf Coast: A Journal of Literature and Fine Art is a leading literary magazine from Houston, Texas. Founded in 1986 by Donald Barthelme and Philip Lopate, Gulf Coast was envisioned as an intersection between the literary and visual arts communities. ...
en.wikipedia.org/wiki/Gulf_Coast_(Literary_Journal)
5-7 inches long with a dome shell. The shell is olive brown or brown and there is very little marking. The back marginal scutes are often flared outward. The plastron is usually unmarked. The skin can be dark brown and the males have colorful heads and forelegs. ...

includes the counties of Dixie, Gilchrist, Levy, Citrus, Sumter, Hernando, Pasco, Pinellas, Hillsborough, Polk, Manatee, Hardee, Sarasota, Desoto, Charlotte, Lee, and Collier.