The vast American continent has been a fertile ground for engineering projects, and the men who engineered them have left their mark on the nation's history. Among them were engineers who spent some or most of their time abroad. John L. McAdam spent several years working in New York before returning to Scotland to develop the "macadam" road surface. Herbert Hoover was a mining engineer before he became a politician, and was known as the "Great Engineer," before the Depression gave him an altogether different reputation.