AR'BOR DAY (Lat. arbor, tree). A day set apart by the legislatures of most of the States and Territories of the United States for the annual planting of trees by the people, and more especially by the school children. B. G. Northrop, while secretary of the Connecticut Board of Education, seems to have been the first—in 1865—to suggest the annual planting of trees under the direction of a State government. J. Sterling Morton was probably the first, however, to propose the setting apart of a certain day annually for the purpose, and in 1872, largely through his efforts, the custom was instituted in Nebraska. At present Arbor Day is observed in nearly every State and Territory; in some as a legal holiday, in others as a school holiday. In addition, several States, including New York, publish an Arbor Day manual. The exact date is not uniform throughout the country, though it generally falls late in April or early in May.