The northernmost of the main islands that comprise Japan
. It's also Japan's largest prefecture
Hokkaido was originally home to an indigenous Caucasian race known as the Ainu. The Japanese gradually displaced them starting around the time of the Meiji Restoration.
Hokkaido is known for its beautiful landscapes and delicious (and inexpensive) food. The weather is very cold in the winter, but is cool and dry in the summer. Many residents of metropolitan areas elsewhere in the country, like Tokyo and Kyoto, visit Hokkaido in the summer to escape the heat and humidity.
Hokkaido's chief exports are seafood, dairy, potatoes, grain and grain-based products, and corn. Hokkaido, especially the cities of Hakodate and Sapporo, is also known for its ramen and beer.
If you go, I suggest getting around by car. The rail service is underdeveloped and sporadic, and you'll end up wasting a lot of time that way. Renting a bicycle and wandering around the fields is very nice. You can stop by at produce stands and eat some corn-on-the-cob or baked potatoes with butter. Yum yum.