The last time several thousand people showed up at the Bethlehem Steel plant in Bethlehem, Pa., they were reporting for a shift at the historic facility, whose 30,000 workers churned out steel for such projects as the Empire State Building and the Holland and Lincoln tunnels. With most work at the plant ceasing in 1995, the 1,600-acre site now is a monument itself, awaiting a major redevelopment that will preserve facilities and draw crowds to SteelStacks, an arts district on the property.