1911 Encyclopædia Britannica/Arbor Day
ARBOR DAY, the name applied in the United States of America to a day appointed for the public planting of trees (see Arbour). Originating, or at least being first successfully put into operation, in Nebraska in 1872 through the instrumentality of J. Sterling Morton, then president of the state Board of Agriculture, it received the official sanction of the state by the proclamation of Governor R. W. Furnas in 1874 and by the enactment in 1885 of a law establishing it as a legal holiday in Nebraska. The movement spread rapidly throughout the United States until with hardly an exception every state and territory celebrates such a day either as a legal or a school holiday. The time of celebration varies in different states—sometimes even in different localities in the same state—but April or early May is the rule in the northern states, and February, January and December are the months in various southern states. A like practice has been introduced in New Zealand.
See N. H. Egleston, Arbor Day: Its History and Observance (Washington, 1896), Robert W. Furnas, Arbor Day (Lincoln, Neb., 1888), and R. H. Schauffler (ed.), Arbor Day (New York, 1909).