The "Hiking with Green Bar Bill" feature was by William Hillcourt, who worked for the editorial department at BSA. He became the best known Scout leader of the last quarter century.
The idea behind "Green Bar Bill" was that it was advice from an experienced patrol leader (the patrol leader's emblem is two green bars). Bill wanted to be anonymous so that the boys reading his column would picture him as a contemporary, rather than an adult. I'm not sure any kids ever bought that, but the moniker was very popular. His column ran until the 1980's, and still appears sometimes, substantially rewritten, in Boys' Life.
He was born in 1900 in Aarhus, Denmark, came to the U.S. in 1926, and died in 1992, in Sweden, on the last leg of a round-the-world trip. The next day of his trip would have taken him back to Denmark for a visit.