At least 20 people died during the bridge’s construction.
The first fatality came in 1869 before construction had even begun. German-born John A. Roebling, who designed the bridge, was taking compass readings one afternoon when his foot was crushed between some pilings and a boat. His toes were amputated, and a few weeks later he died of tetanus. Other workers fell off the 276-foot-high towers, were hit by falling debris or succumbed to caisson disease, better known as “the bends. “No official figure exists for the number of men killed, but estimates range from 20 to over 30. Dozens more suffered debilitating injuries, including Roebling’s son Washington, who became bedridden with the bends after taking over as chief engineer from his father.
Resource is quoted from http://www.history.com/news/10-things-you-may-not-know-about-the-brooklyn-bridge