First - what does Quinta mean? In Portuguese Quinta is a country house (farm) with a small plot of land, where fruit, vegetables and or vines are often cultivated.

How are Quintas (vineyards) classified?
In the Douro region vineyards are graded on a scale A to F with A being the best. This grading system was initially considered in about 1755 but wasn't initiated until after the formation of the Casa do Douro in 1932. Its objective was to promote the production of higher quality wines and to undertake a 'Registration of Property'. The survey was commenced in 1937 and completed in 1945.

 

There are up to 12 qualities that a vineyard is measured on - Location, Aspect, Altitude, Gradient, Nature of land, Soil, Micro-Climate, Vine Varieties, Age if vines, Vine Density, Productivity, Vineyard Maintenance - and each of these qualities are awarded points and the total points gained dictates the grading.
Port is grown and made on these Quintas in the demarcated region of Northern Portugal. This area approximately 1,600 square km's or 242,700 hectares and stretches from 100km's inland from Porto along the river Douro to the Spanish border. The Port growing region is divided into 3 separate areas, each with their own specific meso-climates; the Baixo Corgo, Alto Douro or Cima Corgo and the Douro Superior.

In the past, there were many grape varietals used in Quintas in the Douro region, and farmers chose the grapes that in their opinion were better suited to their particular vineyard. Nowadays there are stricter controls aimed at improving overall quality.
There a six recognized top indigenous grape varietals, plus certain additional approved ones. The top six grape varietals include: Touriga Nacional, Tinta Cao, Tinta Roriz, Tinta Barroca, Touriga Franca and Tinta Amarela.