If you have ever visited Charleston, South Carolina, you may see many of these "earthquake bolts" on the sides of many historic homes and buildings.
Charleston had an earthquake in 1886, the strongest earthquake on the east coast. Many Charlestonian's didn't have the money after the Civil War to repair their homes so they used iron rods with bolts on the ends to pull the homes back together. Most of these bolts are decorative to hide what they actually were used for.