June Hill Robertson McCarroll (June 30, 1867—March 30, 1954) was a nurse (later a physician) with the Southern Pacific Railroad in the early twentieth century who is credited by Caltrans with the simple but revolutionary idea of delineating highways with a painted line to separate lanes of traffic. The concept of painting lines to separate lanes is now in use all over the world.
McCarroll was born and raised in the Adirondacks. She attended a medical college in Chicago, then eventually moved to Southern California in 1904 with her first husband, John Robertson. They had hoped that the desert climate would help him recuperate from tuberculosis, but Robertson died in 1914. Within two years, she had remarried, this time to Frank McCarroll, the local station manager for the Southern Pacific Railroad. From 1907 to 1916, she was the only physician regularly practicing in the vast desert between the Salton Sea and Palm Springs. She was also the only physician serving the five Indian reservations in the area on behalf of the Bureau of Indian Affairs.
In the fall of 1917, McCarroll was driving on the road leading to her office near Indio, California on a stretch of highway that would later be incorporated into U.S. Route 99. The highway remains today as part of Indio Boulevard. She was literally run off the road by a truck, as she recalled many years later:
My Model T Ford and I found ourselves face to face with a truck on the paved highway. It did not take me long to choose between a sandy berth to the right and a ten-ton truck to the left! Then I had my idea of a white line painted down the center of the highways of the country as a safety measure.
McCarroll soon communicated her idea to the local chamber of commerce and the Riverside County Board of Supervisors, with no success. Finally, she took it upon herself to hand-paint a white stripe down the middle of the road, thus establishing the actual width of the lane to prevent similar accidents. Through the Indio Women's Club and many similar women's organizations, McCarroll launched a vigorous statewide letter writing campaign on behalf of her proposal. In November 1924, the idea was adopted by the California Highway Commission and 3,500 miles of lines were painted at a cost of $163,000. Later the idea was adopted worldwide.
A memorial plaque to McCarroll is located at the intersection of Indio Boulevard and Fargo Street in Indio, California. On April 24, 2002, to honor her contribution to road safety, California officially designated the stretch of Interstate 10 near Indio east of the Indio Boulevard/Jefferson Street exit as "The Doctor June McCarroll Memorial Freeway." The plaque is located at GPS coordinates 33º43.260 N, 116º13.040 W.
- Shannon Starr, "Woman credited for highway center lines: Dr. June McCarroll of Indio will be honored with signs on Interstate 10," The Press-Enterprise, 6 April 2002, B3.
- Shannon Starr, "She drew the line toward safer highways: A section of I-10 honors Dr. June McCarroll — but not many know why," The Press-Enterprise, 7 August 2004, B3.
- Starr, "She drew the line," B3.
- Richard Guzman, "Caltrans will honor local motorist who drew the line", The Desert Sun, 24 April 2002, B1.