Why does the Magic Kingdom population 600000000?

if you are referencing to the sign over Main Street station at the entrance to the park, it states "Population 600,000,000 - THE MAGIC KINGDOM (WALT DISNEY WORLD) - Elevation 108ft"

This is the number of estimated guests on June 24 1998. -Disneyland, California in a grand gesture celebrated their 600 millionth guest earlier. So, when the time was approaching for the MK park to do the same they made a celebration out of it.

August 1972 Attendance passes 10 million
March 1976 50-millionth guest
October 1979 100-millionth guest
July 1987 Total attendance tops 250 million
August 1992 400-millionth guest
Oct. 13, 1995 500-millionth guest
June 24, 1998 600-millionth guest

Since marketing have decided not to chronicle total park attendance since then the design of the sign has not changed. average park attendance at the magic kingdom is 17million guests per year so we can safely assume as of 2012 we have surpassed 800 millionth guest mark. next time you pass under the sign be sure to point out "it's more like population 800,000,000". anecdotally as I do! every time.

Now "elevation 108ft" that's a different story all together....