[Jolla]

They measured one of his homers at 550 ft,

When the Yankees were touring the west at the end of spring training in 1951 they played at USC, legend has it rookie Mickey Mantle hit one over 600

[CommerceComet]

There is an interesting site for anyone interested in Mickey Mantle's tape measure home runs and also most anything Mantle-related. The USC home run is #2 on his list of longest home runs and he hit another one that day that was over 500 feet.

Mantle's longest home runs

For the record, I'm not connected with this site in any way, other than just being a Mick fan.