In Walden, Thoreau describes his experiences over two years, two months, and two days in a cabin he constructed close to Walden Pond amid Ralph Waldo Emerson's property near Concord, Massachusetts.

Thoreau makes precise scientific observations of nature as well as metaphorical and poetic uses of natural phenomena. He identifies many plants and animals by both their popular and scientific names, records in detail the color and clarity of different bodies of water, precisely dates and describes the freezing and thawing of the pond, and recounts his experiments to measure the depth and shape of the bottom of the supposedly "bottomless" Walden Pond.

There has been much speculation as to why Thoreau went to live at the pond in the first place. E. B. White stated on this note, "Henry went forth to battle when he took to the woods, and Walden is the report of a man torn by two powerful and opposing drives-the desire to enjoy the world and the urge to set the world straight," while Leo Marx noted that Thoreau's stay at Walden Pond was an experiment based on his teacher Emerson's "method and of nature" and that it was a "report of an experiment in transcendental pastoralism."