[6] The remainder of the tunnel was constructed using the cut-and-cover method, extending from the submerged tubes to the north and south portals.

[7] The tunnel opened on November 29, 1957, with a dedication by Maryland Governor Theodore McKeldin and a crowd of 4,000 spectators.

[9] In the same period, the tunnel also experienced its first collision (15 minutes after opening), first flat tire and first stalled vehicle.

[13][14] In November 2018, the MDTA started a multi-year project to replace the I-895 bridge spans north of the tunnel.

Originally planned to be complete by summer 2021, work was largely finished ahead of schedule in December 2020.

[15][16] After the Francis Scott Key Bridge collapse on March 26, 2024, the Harbor Tunnel became one of the primary alternate routes for drivers and trucks containing non-hazardous loads.