The Cook Block was built by John Ramsey Cook in 1877. Because of the confusion with the Cook Hotel building, which he built in 1869, he renamed the Cook Block the Ramsey Block (for his mother). This building was located at 20 Second Street SW (formerly Zumbro Street). C. F. Massey Company later moved to this location. In 1883, Dr. William Worrall Mayo rented the first floor for his offices, consulting and operating room. The laboratories were on the second floor. Dr. W. W. Mayo and his two sons, Dr. William J. Mayo and Dr. Charles H. Mayo, operated their medical practice in this building until 1901. This building is the earliest location of what would later become the Mayo Clinic.