Take Route 90 (Mass. Pike) East to Exit 24B Route 93 North.
Follow 93 North through the South Station Tunnel, to Exit 23 — Government Center.
The exit ramp takes you out of the tunnel and you will see signs for Faneuil Hall.
At the first light you come to take the left towards Faneuil Hall, and you will now be on North Street.
Take your first right which is Union Street. The Union Oyster House is about 100 yards on the right.