Complex sentence: James J. Curran Jr. took over Lehigh Coal from Bethlehem Mines Corp. in 1989, and through the 1990s it remained the largest producer of U.S. anthracite.
Split into simpler sentences: James J. Curran Jr. takes over Lehigh Coal from Bethlehem Mines Corp. in 1989. Into the 1990s still was the largest producer of U.S. anthracite.