Published in 1854, it details Thoreau's life for two years and two months in second-growth forest around the shores of Walden Pond, not far from his friends and family in Concord, Massachusetts. Thoreau called this an experiment in simple living.
More than a century later, Walden remains a touchstone for Americans seeking to "get in touch with Nature," and is a major cultural icon. It has been parodied in the Doonesbury comic strip, and emulated in Walden Two by B.F. Skinner.
The pond itself is a tourist attraction, as well as a center of controversy over nearby development - thus demonstrating the very tension between natural and man-made pleasures that Thoreau explored in his book.
Walden is also a place in New York State: see Walden, New York.