Founded in 1998, HistoryLink calls itself the “free online encyclopedia of Washington State History” and says it is “the first and largest encyclopedia of community history created expressly for the Internet.” With more than 5,550 original, sourced essays as of March 2010, it is an incredible public resource. The nonprofit site says it serves an average of 5,000 unique visitors a day, one third of whom are K-12 teachers and students.