Grilled pizza was invented in Providence, Rhode Island, by George Germon at Al Forno. Grilled pizza has a thin crust and is cooked quickly--directly on the grate of a grill. Contrary to what you'd think, it does not fall through the grate, instead setting up quickly over the intense heat before being flipped and topped with sauce and thinly sliced toppings. (Toppings must be thin so they heat through in the short time--typically a minute a side. Sausage or anything needing thorough cooking need to be prepped beforehand.)

Grilled pizza has since moved beyond Providence--there are at least five such pizzerias in New York City, and the in the last three or so years we've seen this dish move from obscurity to backyard grills nationwide, thanks to the annual grilling coverage in magazines and newspaper food sections that crops up around Memorial Day.

Related

Grilled Pizza archives [Slice]

Grilled pizza [Wikipedia]