Erie, Pennsylvania is the Commonwealth's primary access point to Lake Erie, the Great Lakes, and the Saint Lawrence Seaway. The city developed first as a maritime center after the American Revolution, as a railroad hub during the great American westward expansion, and as an important manufacturing center during the Industrial Revolution. By the 21st century, electric locomotive building is all that remains of big industry, but smaller-scale steel and plastics manufacturers, as well as health care, insurance, tourism and recreation have emerged as Erie's new diverse mix of key industries.