A sweet fortified wine most often served after a meal. Grape alcohol is added to the wine partway through fermentation, stopping the process at a point where the wine has plenty of sweetness and alcohol (18 to 20 percent). Port wines originated in the Douro Valley in northern Portugal; the best ports still come from that area. The name is derived from the fact that these wines are shipped out of the Portuguese city of Oporto and, in fact, such wines are labeled "Porto," rather than "port. " There are many types of port and the various labels can be confusing. The best and most expensive are Vintage Ports, which are made from grapes of a single vintage, bottled within 2 years. The very best of these can age 50 years or more. Late-bottled Vintage Ports and Single Vintage Ports are also made from grapes of a single vintage (though the grapes are not of as high a quality as those for vintage Ports). Late-bottled Vintage Ports are aged in wood for up to 6 years, while Single Vintage Ports have been wood-aged at least 7 years. Both are ready to drink when bottled and do not have the aging potential of Vintage Ports. Tawny Ports are a blend of grapes from several different years and can be aged in wood for as long as 40 years. They're tawny in color and ready to drink when bottled. Vintage Character Ports are essentially high-quality Ruby Ports, which are considered the lowest grade of port. They're blended from several vintages and wood-aged, but not nearly as long as Tawnies. They're the lightest and fruitiest in flavor and are ready to drink when bottled. American wineries have been bottling vintage ports since the early 1970s.