The Institute for Supply Management says its manufacturing index read 58.4 in January, compared with 54.9 in December. December's figure was revised lower from 55.9. Analysts polled by Thomson Reuters had expected a level of 55.5. A reading above 50 indicates growth.
New orders, a sign of future growth, jumped to their strongest level since 2004.
Manufacturing has helped lead the U.S. economic recovery as companies replace depleted stockpiles, and a weak dollar boosts exports to fast-growing countries in Asia and Latin America.
