In the late 1800s, Nebraska newspaper editor J. Sterling Morton tapped into settlers’ longing for shade in the sunbaked territory and used his paper to promote planting trees. He later became a state leader and created Arbor Day in 1872 specifically for tree planting. By the 1920s, 45 states were celebrating, and President Richard M. Nixon made it a national holiday in 1970. Trees have extensive environmental and economic value, and urban tree cover has particular importance: Research shows it can lower energy costs, clean the air and mitigate potentially damaging stormwater runoff.
Sources: States, Puerto Rico, American Samoa, Guam, Northern Mariana Islands, US Virgin Islands