The money was buried by Michael in a location known only to him, as a means to secure their financial freedom once they escaped from Fox River State Penitentiary.

The money became a 'MacGuffin' - a plot device that motivates the characters but ultimately, its importance diminishes as the series progresses.

by Michael, Lincoln, and Sucre in episode 2.04 (“First Down”). They dig it up at the billboard in Oswego. However, they’re ambushed by the manhunt. The money changes hands rapidly:

The $5 million from Prison Break ultimately ends up confiscated by federal authorities after being found by a civilian in the Utah desert. It serves as a tragic irony: the money that everyone killed, betrayed, and died for never benefits any of the protagonists—and only enriches the government they were running from.

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