Armstrong, a W. county of Pennsvlvania, intersected and partly bounded by Alleghany river; area, 750 sq. m.; pop. in 1870, 43,382. The surface is undulating and the soil gener-ally fertile. The Pennsylvania canal passes through its southern extremity. Its most valuable mineral productions are iron, salt, and coal. In 1870 the county produced 298,194 bushels of wheat, 135,257 of rye, 680,314 of Indian corn, 883,846 of oats, 33,192 tons of hay, 126,068 lbs. of wool, and 964,020 of but-ter. Capital, Kittanning.