[rprasad]

Wikipedia is wrong on this subject, unless you greatly expand the legal definition of gambling. The gambling prohibition passed around the same time as the alcohol prohibition, but survived because it grandfathered existing gambling locales (Nevada, Atlantic City, Washington, and Delaware, generally, though the latter two have since outlawed or restricted gambling.)

This is why there are no casinos (other than indian casinos) outside of Nevada, Atlantic City, and reservations. Do you really think that California wouldn't have a billion casinos (in addition to the Indian Casinos) if they weren't prohibited from doing so by federal law?

Gambling generally means any wager for cash, where skill does not play a role in the chance of winning the prize. Skill generally applies to intermediate steps en route to winning, not "skill" in selecting the prize-winning item. This includes lotteries and horse racing, but these forms of gambling are specifically excepted from the gambling prohibition. Most traditional casino card games are considered games of "skill" rather than gambling, which is why card houses are legal (subject to local restrictions).

Sports books are legal, so long as they are based in a state where gambling was legal when the gambling prohibition took affect.

[demachina]

You are incorrect. Casino gambling is entirely state regulated, there is no Federal law controlling it. More and more of them are allowing it because its an easy way to boost their tax revenues without raising income and property taxes.

The Mississippi gulf coast has had casino gambling since the 1990's when it was authorized by the state, http://www.worldcasinodirectory.com/mississippi.

Colorado voters legalized casino gambling in BlackHawk in the 1990's as well, http://www.blackhawkcolorado.com.

Detroit legalized gambling in the 1990's, and a number of state legalized it on riverboats on the Mississipi in the 90's as well.

The Federal laws on the subjects mostly apply to interstate gambling enterprises which is where they do have jurisdiction, in particular sports betting and the 2006 law which outlawed online gambling primarily by preventing banks from transferring funds to and from online gambling sites.