It is generally agreed that the modern gay rights movement in the United Stated and in the world (the earlier attempts in Germany fizzled due to the Nazis) started with the Stonewall Riots in New York in 1969.  Despite this, the United States presents somewhat of a paradox for the GLBT traveler.  While it has probably the largest organized GLBT community in the world, it's legislation is not as friendly towards GLBT people as in other countries such as the western part of the EU and Canada.  Also, there is a great regional disparity in the United States on how GLBT people are viewed and accepted.

In general, you will have no problems in the larger coastal cities in the West and Northeast (Boston, New York, San Francisco, Washington, Los Angeles, Seattle).  Be aware, however, that gay-bashing does exist in all of these places, and can be more pronounced in gay bar areas, as bashers often target people near gay and lesbian bars.  It is best to go with someone if planning a night on the town and if alone and returning from a gay bar, it is usually best to drive or use a cab.  If on foot, try to avoid being seen leaving a gay bar on a main thoroughfare and then walking into a more dimly lit side street, as many bashings occur that way.  This is true not just of these cities but anywhere in the USA.

In other large cities, there are usually large and friendly GLBT communities.  This would include places such as Chicago, Atlanta (sometimes known at "Hotlanta"), Houston, Dallas, etc.  However, in these places openly GLBT folks may not mix as easily with the straight population, especially outside the workplace where close friendships between GLBT's and straights may be a bit less common than on the coasts, though by no means non-existent.

In medium sized cities, especially inland ones, there will be some bars and community resources though not to the extent of larger towns.

Public same-gender displays of affection are usually not accepted in the USA outside of gay villages such as the Castro in San Francisco.  Reactions elsewhere could range from either stares or looking away to outright violence.

GLBT people need to be more careful and, in some cases, hide their sexual orientation, when traveling through rural areas, especially in the southern states.  These areas may be very conservatively religious and not accepting.  In general, it's best to feel people out before bringing up  sexual orientation in conversation.  Also, all public displays of affection should be avoided and same-gender couples need to be careful about using terms of endearment for one another where they can be overheard.

There are zillions of GLBT travel guides to the USA.  In addtion to large cities (especially San Francisco), there are a number of specialized GLBT-friendly destinations.  These include resorts and smaller cities known for their tolerance.  Of these, probably some of the most well known are Ogunquit, ME: Provincetown, MA; Fire Island, NY; Rehoboth Beach, DE; Orlando, FL; Fort Lauderdale and Wilton Manors, FL; New Orleans, LA; Saugatuck/Douglas, MI; Santa Fe, NM; Palm Springs, CA; and the Russian River area, also in California.   Specialized travel guides exist for gay men, lesbians and even gay naturist travelers.