Aroostook, a county comprising the N. and' N. E. portions of Maine, and bordering on the provinces of Quebec and New Brunswick; area, 6,800 sq. m.; pop. in 1870, 29,609. The surface is undulating, with a few mountain peaks, the loftiest of which are Chase's Mount and Mars Hill. The St. John's river forms the N. boundary and flows through the W. part of the county, and is navigable for vessels of 50 tons. It is also watered by the Aroostook, a W. tributary of the St. John's, Allagash, Mat-tawamkeag, and several smaller rivers; and there are many small lakes and ponds. The soil is generally very fertile, but a great part of the surface is still covered by pine forests. In 1870 the county produced 46,946 bushels of wheat, 532,151 of oats, 360,450 of buckwheat, 380,701 of potatoes, 48,052 tons of hay, 86,-173 lbs. of wool, 523.510 of butter, and.53,-186 of maple sugar. Capital, Houlton.