For his groundbreaking 1948 LIFE magazine photo essay, “Country Doctor” — seen here, in its entirety, followed by several unpublished photographs from the shoot — photographer W. Eugene Smith spent 23 days in Kremmling, Colo., chronicling the day-to-day challenges faced by an indefatigable general practitioner named Dr. Ernest Ceriani.

Six decades later, Smith’s images from those three weeks remain as fresh as they were the moment he took them, and as revelatory as they surely felt to millions of LIFE’s readers as they encountered Dr. Ceriani, his patients and his fellow tough, uncompromising Coloradans.

Born on a sheep ranch in Wyoming, Dr. Ceriani attended Chicago’s Loyola School of Medicine but opted not to pursue a medical career in the big city. In 1946, after a stint in the Navy, he was recruited by the hospital in Kremmling, and he and wife Bernetha, who was born in Colorado, settled into the rural town. Dr. Ceriani was the sole physician for an area of about 400 square miles, inhabited by some 2,000 people.

William Eugene Smith (December 30, 1918 – October 15, 1978), was an American photojournalist, renowned for the dedication he devoted to his projects and his uncompromising professional and ethical standards. Smith developed the photo essay into a sophisticated visual form. His most famous studies included brutally vivid World War II photographs, the clinic of Dr Schweitzer in French Equatorial Africa, the city of Pittsburgh, the dedication of an American country doctor and a nurse midwife, and the pollution which damaged the health of the residents of Minamata in Japan.