It is thought that yodeling was first introduced to the United States by German immigrants in Pennsylvania in the early 1800s. As the new settlers traveled south through the Appalachian Mountains and beyond into the Deep South they came into contact with Scots-Irish immigrants, Scandinavians (practitioners of a unique yodeling called kulning), and other nationalities including African slaves who communicated with "field hollers", described by Frederick Law Olmsted in 1853 as a "long, loud, musical shout, rising and falling and breaking into falsetto".