Before the Civil War, wines from the island of Madeira were prized above all others in the United States. The Declaration of Independence was toasted with Madeira. Washington and his officers are said to have consumed 54 bottles of Madeira in one night at a tavern in Philadelphia.
Madeira is a fortified wine (like Port) that is made from a variety of grapes, each corresponding with a different level of sweetness. The Sercial grape is used to make the driest (aka least sweet) style. Malvasia or "Malmsey" is used to make the sweetest wines. In between is the Bual or "Boal" grape that is used to make slightly sweet wines that also have refreshing acidity.
Unlike Port, Madeira is virtually ageless and indestructible. I typically open a special older Madeira before Christmas and enjoy a taste throughout the year. 100% Bual. Serve cool. Ideally in smaller sherry or Port glasses.