January 27, 2012 is the first official Port Day...
As Center for Wine Origins who is behind this initiative reminds us this unique wine, Port, "comes exclusively from Portugal’s Douro Valley".
Nevertheless some wineries in California, Australia and other places still call their port style fortified wines 'port wines'.
An example is Revolution Wines in Sacramento (California) with their 'St Rey Single Quinta Ruby Port'.
Should they call it Port style instead?
American producers of these type wines have an umbrella organization called Sweet and Fortified Wine Association
whose site shares a few historical facts on Port and details on port styles (reproduced below):
"What is Port?
Port is a fortified wine originating from the Douro Valley in Portugal. The wine takes its name from the Atlantic coast city of Oporto at the mouth of the 560-mile long “River of Gold”.
The Romans introduced wine to the Iberian Peninsula in the first century B.C. But it wasn’t until the 17th-century that the British added brandy to the harsh red wines of the Douro to stabilize them for shipment to England. The ongoing wars in Europe affected the ability of the British to obtain their favored “clariet” wines from France so they looked to Portugal as a reliable source of drinkable red wine.
The first English port house was established in Oporto in 1670. In 1703 the British and Portuguese signed the Methuen Treaty that paved the way for the port trade that exists to this day.
While there are port-style wines made around the world from Australia to South Africa to California, strict use of the term Port is reserved for fortified wines produced in Portugal.
Over 500 grape varieties are grown in Portugal but only 30 different varieties are found in the Port wine region of the Douro. Of these, only five are considered to have the exceptional quality for Port wine. These varieties are Touriga Nacional, Tinta Roriz (Tempranillo), Tinta Barroca, Tinto Cao, and Touriga Francesa.
Much of the grape harvesting along the steep slopes of the Douro Valley is still done buy hand. Grapes were traditional trodden barefoot in open granite lagers but today most of the crush is done mechanically. The must is placed in concrete or stainless steel tanks for fermentation. When about have the grape sugar has been turned to alcohol, the juice is run off into barrels containing about brandy which stops to fermentation. The usual mix is one part brandy to four parts juice.
In the spring following harvest, the wines are moved down the Douro Valley to Vila Nova de Gaia where blending, aging, and bottling takes place. There are many different styles of Port but two broad categories – bottle aged or cask aged. Bottle aged Ports are aged for a short time in oak then bottled unfiltered to age to maturity. These Ports retain the color and fruitness into maturity. Cask aged Ports are aged in wood then filtered and bottled. While cask aged Ports become tawny in color, they are ready to drink on release."
To (i am sure) the chagrin of Center for Wine Origins, they follow this nice introduction with chapter on 'American Port'.
While looking for details on Port, i found the Port Wine 'Times Reference' page which includes a Port Navigator and an archive of articles on topic in NY Times.
I suggest you pay that page a visit. You will emerge rich with knowledge.
Happy Port Day!