Where was Thoreau in 1850?
To find out, look on line 33 of this page from the 1850 census taken in Concord, Massachusetts. It reveals that Henry David Thoreau—the author of Walden—was 33 years old and living at home with his parents. The 1850 census was the first one that listed individuals instead of families and that included questions about place of birth, age, and occupation.
National Archives, Records of the Bureau of the Census