MD: For snakes and lizards, a permit required for more than 4 of native snakes in list A (check the regulations for Captive Reptile and Amphibian Permit at the MD Department of Natural Resources Wildlife & Heritage webpage) or if you breed native snakes. This includes corn snakes. The permit is a flat fee of $25 annually, but it does give DNR permission to inspect the buisiness or home indicated on the permit.
MD DNR does not regulate non-native snakes, but by MD law venomous snakes are illegal, as are alligators, caiman, and crocodiles.
Some cities/counties have bans on large snakes and lizards. Baltimore city does not allow a snake or lizard over 5 feet. If I had a snake larger than a boa in Howard County, I'd keep it quiet.
In DC, lizards are illegal but snakes are legal.
In PA, almost anything is legal except native reptiles. Check city and county ordinances, though.
Katrina
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1.2 Eastern Muds - Fred, Ethel, Edith
0.1 Iguana - Tiffel
0.1 Bearded Dragon - Foster
Foster turtles: More than I'd like the husband to know about.