Henry David Thoreau first publishes Walden.

Henry David Thoreau published only two books during his lifetime: A Week on the Concord and Merrimack Rivers and Walden, or, A Life in the Woods. Thoreau began A Week when he went to live at Walden Pond in 1845. Intended to be a memorial to his older brother John, who had died of lockjaw three years earlier, the book was based on a boat trip they had made together in 1839. On the website dedicated to the writings of Thoreau at the University of California, Santa Barbara, Elizabeth Witherell and Elizabeth Dubrulle describe how the creation of A Week ended up overlapping with Walden:

At Walden, Thoreau worked diligently on A Week, but he also explored Walden Woods and recorded his observations on nature in his Journal. He entertained visitors and made regular trips to town; friends and neighbors began to inquire about his life at the pond. What did he do all day? How did he make a living? Did he get lonely? What if he got sick? He began collecting material to write lectures for his curious townsmen, and he delivered two at the Concord Lyceum, on February 10 and 17, 1847. By the time he left the pond on September 6, 1847, he had combined his lectures on life at Walden with more notes from his journal to produce the first draft of a book which he hoped to publish shortly after A Week.

Unfortunately, A Week sold only two hundred copies during the first years after publication. In a Journal entry of October 28, 1853 (PDF) Thoreau describes receiving from the publisher “in a wagon” 706 copies of its printing of 1,000.