A U-Haul got stuck while unloading the tires near the Centennial Arboretum.
Park rangers came upon the massive mess, just off Belmont Avenue and behind the Ohio house, on Sunday evening.
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They found the U-Haul completely empty, with about 300 tires left behind it.
There were also roughly 500 more tires dumped about 500 yards away.
The people responsible took off and left the pile behind.
Officials say the U-Haul was reported stolen, but it's not clear when.
Illegal dumping has been such an issue that a new program is targeting the problem.
"Really, we're looking for these huge piles that contractors or private citizens might leave here," said Illegal Dumping Ambassador Daniel Lidon.
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The Park Ambassadors project, funded by the William Penn Foundation, is a two-year pilot program aimed at curbing illegal dumping by 50%.
"Our park ambassadors will collect evidence; sometimes we have camera footage to support that evidence," said Illegal Dumping Prevention Coordinator Nathan McWilliams.
The goal is not only to clear it, but to prevent it, including by implementing steep fines to deter litterbugs.
Illegal dumping can carry fines of up to $5,000 per piece of material.
The space at Fairmount Park is cleared, but now the work begins on tracking down the person behind the wheel and any accomplices.