There are currently more than 750 such areas in the National Wilderness Preservation System comprising over 109 million acres -- roughly 5% of the United States by area. Need a refresher from the other 95%? The Active Times picked 10 wild places in the lower 48 states that are truly wild.
Polio, which struck children disproportionately, could attack the central nervous system and cause muscle deterioration, paralysis and even death. American virologist Jonas Salk, who was born 100 years today on October 28, 1914, developed the worldâs first safe and effective polio vaccine.
Polio has been eradicated in the U.S., but there are still cases in several other countries. The last U.S. case was reported in 1979. Evening Edition host Peggy Pico speaks with Charlotte DeCroes Jacobs, author of Jonas Salk: A Life, about the new biography that explores the many facets of the man.