Walnut Grove Post Office was the post office in Walnut Grove.
The Post Office was located in the same building as Doctor Baker's office. It was normally managed by Melinda Foster but has been managed (at different times) by Alice Garvey, Grace Edwards, and once Mrs. Whipple (temporarily) (Episode 409: The High Cost of Being Right), and for some reason Kezia later on. (Episode 519: The Lake Kezia Monster) Kezia had a habit of snooping in other people's mail. In the same building was Doctor Baker's office, the Post Office also had a few rooms up for rent which Doctor Baker would sometimes use for sick patients. At one point Nels Oleson and Harriet briefly separated and Nels briefly moved into the Post Office rooms. (Episode 117: Family Quarrel).
The Post Office was destroyed along with the rest of the town in 1901.