North American beaver, Castor canadensis, reached an estimated maximum population of 60-400 million individuals. To put that in perspective, the current population of the United States is 319 million individuals. That’s a lot of beavers!
Unfortunately, by 1900 the population had been pushed nearly to extinction.
This was due almost exclusively to the booming fur trade in North America in the 1700s and 1800s. European felt hats were in high demand, and there was a lot of money to be made beaver trapping. Luckily, public concern over the rapidly declining beaver population led to policy changes regulating trapping beaver and also put forward programs for reintroducing beaver to their former range. These efforts proved very successful in the past century: the current North American beaver population is estimated to be between 10 and 15 million individuals and growing!