The people I grew up around called all spoted cur dogs leopards. In La. and Miss. they called the spoted dogs leopards and the solid colored dogs catahoulas. Now days, the spoted stock dogs are catahoulas and the american leopard curs are the east coast, open on track, tree dogs. They are said to of been around for many years but were very rare untill Richard McDuffie brought them back starting in the 60's. The funny part is, the three main dogs he used came out of Texas. A reliable source told me they came from Cowboy Williams and were July Catahoula crosses. That might be the reason for the double coat. The UKC registers the as American Leopard Hounds.
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I wrote an article on this very topic:
http://thehoundsmen.blogspot.com/2008/12/catahoula-or-leopard-cur-dog-or-hound.html