The Portuguese island of Madeira juts out of the Atlantic Ocean, a mass of volcanic precipices marked by tiny patchwork vineyards carved into its steep slopes. From these vineyards comes Madeira, the fortified wine that is like no other wine in the world.

More than two centuries ago, Madeira was the celebratory libation of choice at such auspicious occasions as the signing of the Declaration of Independence and the inauguration of George Washington. Thomas Jefferson frequently served the distinctive wine at the White House. But tastes change, and today few people know that Madeira is one of the world’s longest-lived wines.

Among the island’s most prominent shippers is the Madeira Wine Co., an association of four historic producers: Cossart Gordon, Leacock’s, Blandy’s and Miles. Other labels of note are Justino Henriques Filhos, d’Oliveira, Quinta de São and João Baptista.

Traditionally, fine Madeira has been made from one of four classic white-grape varieties. Sercial, the driest, is smooth and pale, with a keen, lively taste; it is often served chilled as an aperitif. Verdelho is golden and medium dry with a bright, vivid flavor. Bual (Boal in Portuguese) is sweet, satiny and darker, a wine to serve with dessert or with a pungent cheese. Malmsey, the sweetest and darkest Madeira, is full-bodied and rich, a dessert in itself. All Madeira share a vibrant, refreshing acidity. Another classic grape, Terrantez, is only rarely planted today. If you see one of its wines, buy it, as it will be an extraordinary experience. Vintage Madeira, produced only in exceptional years, is aged a minimum of 20 years in the cask and usually two more in the bottle before being released. Even then, it is considered a baby.

Along with the classic grapes, the red grape Tinta Negra Mole has been heavily planted since early last century. The reason: It grows easily and quite prolifically. Tinta Negra Mole accounts for much of the lesser-priced Madeira, such as the generic vintage called Rainwater.

But it is the classics that speak best for Madeira. Open a bottle and pour a sip each evening, and when you come to the last sip a month or two later, it will be just as flavorful as the first. Madeira is its own fountain of youth.