Police said an investigation led officers to the yard in Burton, north of Adelaide, at about 10.30am yesterday.
Detectives found allegedly stolen vehicles, earthmoving equipment, horse buggies and about 20 shipping containers.
Numerous trucks, industrial trailers, bobcats, four-wheel-drives and forklifts were also found among the haul.
Police said it is estimated that it will take several days to go through the property, match it to theft reports and return items.
“The volume is significant, we’re talking 20 shipping containers containing various items,” Chief Inspector Andrew McCracken said.
“Some of the forklifts and other things (are) valued in excess of $200,000, bobcats $160,000, (a) LandCruiser $200,000, so it mounts up very quickly.
“We are currently doing a search in groups methodically to thoroughly investigate and try and locate owners of property.”