Arbor Day was created in 1872 to promote planting trees on the Nebraska plains, thanks to journalist Julius Sterling Morton, who championed the idea after he bought a large plot of Nebraska land. Tree planting became prominent in schools by the 1880s, and by 1920, nearly every state and territory had designated an Arbor Day. President Richard Nixon declared the fourth Friday in April a national Arbor Day in 1970. To mark the holiday this year, Map Monday shows the official trees in each state and territory. Sources: American Samoa territorial tree, Guam territorial tree, History, Northern Marina Islands territorial tree, Puerto Rico national tree, U.S. Virgins Islands territorial tree, USA Today