The Salvador Dali museum in St. Petersburg, Fla. (Photo by Flickr user Matthew Paulson, used under a Creative Commons license.)There are roughly 11,000 Starbucks locations in the United States, and about 14,000 McDonald's restaurants. But combined, the two chains don't come close to the number of museums in the U.S., which stands at a whopping 35,000.So says the latest data release from the Institute of Museum and Library Services, an independent government agency that tallies the number and type of museums in this country. By their count the 35,000 active museums represent a doubling from the number estimated in the 1990s. While most of us think of massive institutions like the Smithsonian and the Guggenheim when we think of museums, one lesson of the new data is that the majority of U.S. museums are small, nearly mom-and-pop affairs. Of the roughly 25,000 museums with income data in the file, 15,000 of them reported an annual income of less than $10,000 on their latest IRS returns.