The occupation began on January 14, 1987, and lasted 103 days. It ended on April 26 after the American makers of earth moving equipment obtained an eviction order.
Weeks before, Caterpillar executives had announced an upgrade costing more than £70million - only to change their minds and declare their Scottish manufacturing base was to close and production switched to sister plants in Europe.
Workers were furious, while politicians called it a betrayal. Caterpillar's only Scottish site made giant bulldozers. Production began in 1956 and at its peak the plant employed 2700. Three decades later the Tannochside complex, near Uddingston, North Lanarkshire, fell silent when production halted on October 28, 1987.
Tributes were to be led by local councillors and former Caterpillar shop steward Bob Burrow at the new memorial just yards from the original site.