When the Salk polio vaccine rolled out in North Dakota in 1955, children ages 5 to 9 and pregnant women were given top priority. Parents welcomed the vaccine with open arms. Polio could paralyze and even kill, and young children were the most vulnerable. The National Foundation for Infantile Paralysis, which led the March of Dimes for vaccine research and patient care, provided the vaccine free of charge for first- and second-graders. Salk’s vaccine came in a series of three shots. By the end of 1955, 59 percent of those children in North Dakota were vaccinated. None contracted polio.