 The 1760s Gardiner Building, once home to John Hancock's counting house and now a Chart House restaurant, is the wharf's oldest surviving structure.Among several similar structures, a grand granite warehouse known as the Custom House Block was built in 1848 atop the wharf; it has survived into the 21st century.The mid-19th century was the height of Boston's importance as a shipping center, lasting roughly until the American Civil War.