Squirrels seem to be as natural a part of America's cities as concrete and steel, but in reality the critters are another one of humans' additions to the urban environment. The grey squirrel that thrives in the majority of the United States, for example, is native to the Northeast, and was sometimes kept as a pet during the colonial era. Benjamin Franklin even brought a squirrel -- which he called Mungo -- with him to England; when Mungo died, Franklin wrote the animal a eulogy.
But when rapid urbanization began in the 1800s, squirrels flocked from the city to the forest. They were virtually eradicated from New York just before the Victorian era, but when Central Park opened in the mid-19th century, squirrels were reintroduced as a form of entertainment. Of course, they quickly came to be seen as a nuisance, Sadie Stein reports in her detailed timeline of squirrels in the city -- though not to everyone. Here are some highlights from Stein's history of our squirrely relationship with these animal urbanites: