Story highlights Joe Sheahan's father is buried on the site known to many Americans as the mysterious Area 51; his family goes back generations there

Sheahan and his family are fighting the Air Force over rights to the land in the Nevada desert

Rachel, Nevada (CNN) For decades the public has tried to find out what's buried at Area 51, the military facility that housed America's top Cold War secrets.

For Joe Sheahan, it's his father -- buried on a plot of land three miles from where the U-2 spy plane was perfected, according to CIA documents declassified in 2013.

This week, Sheahan visited his father's grave site for what he thinks will be the last time, now that the U.S. Air Force wants to buy the land and has vowed to use eminent domain to get it. The Sheahan family, which has owned the land in southern Nevada since the 1880s, doesn't like the government's price: $5.2 million for 400 acres of land and mining rights.

The Sheahan family has owned Groom Mine, a piece of land in Area 51, for more than 125 years.

A September 10 deadline to accept the offer has passed with no agreement, and Joe Sheahan is digging in for a legal fight.

"If I come out with nothing, so be it," he told CNN. "I'm not going to lay down and say it's OK."

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