Even before Columbus came to America, Europeans believed that the Promised Land lay to the west. For example, Genesis 4:16 says:
And Cain went out from the presence of the Lord, and dwelt in the land of Nod, on the east of Eden.
As the American eastern seaboard became overpopulated and the land worn out, people simply moved further west to a new promised land.

In the 1840-50s, the blight-induced Irish potato famine resulted in a 20% drop in Irish population. Many died of starvation, but many more emigrated to Canada, Britain, the US, and Australia. Heavy Irish emigration to America continued into the first quarter of the 20th century, long after the famine was over. The conflict over leaving family behind to go to the new world is the subject of Barney McCoy, performed by Uncle Eck Dunford, lead vocal, and Hattie Stoneman (sic), harmony vocal, with fiddle, guitar & harmonica (...or so say the discographers. I hear Ernest Stoneman's rather than Hattie's voice on the harmony part). Recorded July, 1927 in Bristol, Tennessee by the Victor Company. Reissued 2006 on a 4-CD set, Serenade in the Mountains, JSP 7780. That recording is available several places on the internet, such as http://www.elderly.com/recordings/09A.htm. The song was copyrighted by one J. Murphy in 1881, although it reportedly dates from the 1870s. For more commentary, lyrics and music, see http://www.lizlyle.lofgrens.org/RmOlSngs/RTOS-BarnMcCoy.html. Hattie Stoneman, mother of the members of The Stonemans bluegrass band, is probably playing fiddle on this song. She was less well known than her husband, Ernest, but was an expert fiddler and singer in her own right. Alec (Eck) Dunford was her uncle.

The conflict between the need to move and family ties wasn't limited to Ireland. Another example: I'm Going to the West, performed by Peggy Seeger, lead vocal and autoharp; Mike Seeger, harmony vocal and mandolin; and Penny Seeger, harmony vocal and lap dulcimer. Recorded 1989 in Maryland for Folkways Records and re-released as Smithsonian-Folkways CD 40048, Peggy Seeger: The Folkways Years, 1955-1992. Peggy arranged the song from a book, Byron Arnold's The Folksongs of Alabama (University of Alabama, 1950). Arnold's informant thought the song was from the 1880s, when lots of Alabamans moved west to Texas. For more commentary, lyrics and music, see http://www.lizlyle.lofgrens.org/RmOlSngs/RTOS-GoingWest.html.

Even when you get to the Promised Land, you can get into trouble if you do something stupid, as described in When First Unto This Country A Stranger I Came, performed by Mike Seeger, vocal & autoharp, and Tom Paley, banjo. First released on Folkways LP FA2397, The New Lost City Ramblers, Vol. 2. Re-released on Smithsonian-Folkways CD 40036, The New Lost City Ramblers: The Early Years, 1958-1962.  The Seegers' source was Foy and Mrs. Maggie Gant, recorded 1934 in Austin, Texas, by John & Alan Lomax (Library of Congress Archive of Folk Song #65A2). The Gant family recorded several unusual songs for the Lomaxes. We have no idea where this song came from or what happened to any of the Gants. For more commentary, lyrics and music, see http://www.lizlyle.lofgrens.org/RmOlSngs/RTOS-WhenFirst.html.

During World War I, the US encouraged farmers to grow more wheat by subsidizing its price. It worked. A large amount of prairie land was plowed under for wheat. When the government suddenly stopped the subsidies in the early 1920s, there was a severe farm recession. The farmers naturally responded by tilling even more land to make up for it, a further demonstration of the Law of Unintended Consequences. When the drought of the 1930s hit the great plains, the denuded land blew away to form the infamous Dust Bowl. Between 1930 and 1950, the population of the US increased by 31% while the population of Oklahoma fell by 7%. Where did all those people go? To California. There's bound to be difficulties when the Promised Land is already overcrowded. An ironic take on the situation is given by Dear Okie, performed by the New Lost City Ramblers: John Cohen, vocal & guitar; Tracy Schwarz, fiddle; and Mike Seeger, banjo. First released on Folkways LP 31027, Modern Times, and re-released on Smithsonian-Folkways CD 40040, The New Lost City Ramblers Volume II, 1963-1973: Out Standing in Their Field. The song was first recorded by country singer Doye O'Dell in 1948.

A more heartfelt commentary on the Okie migration is California Cotton Fields, sung by Hazel Dickens, with bluegrass band accompaniment. Originally released on Rounder LP 0226, It's Hard to tell the Singer From the Song, released in 1988. Available as a CD at http://rounder.com/index.php?id=album.php&musicalGroupId=484&catalog_id=60470126. The song was written by country-western composer Dallas Frazier.