The publication in 1934 of the first modern field guide by Roger Tory Peterson revolutionized birding. However, in that era, most birders did not travel widely. The earliest known continent wide big year record was compiled by Guy Emerson, a traveling businessman, who timed his business trips to coincide with the best birding seasons for different areas in the North America. His best year was in 1939 when he saw 497 species. In 1952, Emerson's record was broken by Bob Smart, who saw 510 species.
In 1953, Roger Tory Peterson and James Fisher, took a 30,000 mile road trip visiting the wild places of North America. In 1955, they told the story of their travels in a book and a documentary film, both called Wild America. In one of the footnotes to the book Peterson said "My year's list at the end of 1953 was 572 species." In 1956 the bar was raised when a twenty-five year old Englishman named Stuart Keith, following Peterson and Fisher's route, compiled a list of 598 species.
Keith's record stood for 15 years. In 1971 eighteen year old Ted Parker, in his last semester of high school in southeastern Pennsylvania, birded the eastern seaboard of North America extensively. That September, Parker enrolled in the University of Arizona in Tucson and found dozens of Southwestern U.S. and Pacific coast specialities. He ended the year with a list of 626 species. (Before his death in 1993, Parker went on to become one of the world's most renowned field ornithologists, and the acknowledged leading expert on the birds of the American tropics.)
Another notable record was set in 1979 by James M. Vardaman as recorded in his book Call Collect, Ask for Birdman. Vardaman saw 699 species that year and travelled 161,332 miles (137,145 by airplane; 20,305 by car; 3,337 by boat; 160 by bicycle; and 385 by foot).
The big year of 1998 was the subject of a book of the same name by Mark Obmascik. In that year three different birders, Sandy Komito, Al Levantin and Greg Miller, chased the record of 721 birds, held by Komito. In the end Sandy Komito kept his record, listing an astonishing 745 birds, a record many in the birding community believe might never be broken. The reason they believe this is because during that year, one of the strongest El Niño years on record caused many lost rare birds to come to North America. North America itself has only about 675 native species.