Where does sushi come from?
Japan! While the origins can be traced to areas outside Japan, today's modern sushi began in 19th Tokyo (then known as Edo) with the invention of nigiri. As a form of fast food, it quickly spread throughout Japan.
How did it get to America?
Sushi came to America with Japanese immigrants in the early 1900s. It became popular in the late 20th century through sushi restaurants in major cities, such as New York and Los Angeles. Furthermore, it gained popularity with the appearance of other non-traditional items, such as the California Roll, which was invented in Los Angeles and can be found in virtually every sushi restaurant in North America today.
What is the future of sushi?
While sushi will certainly continue to become more popular and creative, one major concern is sustainability. In fact, the popularity of sushi has led to overfishing of many popular choices, such as tuna. Additionally, there are indirect effects on other species that may be used as feed at large fish farms. Many restaurants already advertise that all their items are sustainable, meaning that they can be harvested and regrown indefinitely, and other locations even try to popularize some of the lesser known fish to keep any one species from becoming too overused. There are many challenges ahead in this area, especially as sushi becomes more popular in areas such as China and demand continues to grow.
Where can I learn more?
Wikipedia has some great resources on sushi and its history. For more information on sustainability, you might try watching Sushi: The Global Catch. Also, another enjoyable documentary that shows just how serious sushi can be is Jiro Dreams of Sushi.