Answer: Elephants

When the Brooklyn Bridge opened in 1883, it was to an enormous amount of fanfare and excitement. Thousands of people attended, the then-President of the United States Chester A. Arthur was in attendance, and the procession was accompanied by fireworks and cannon fire. On the first day alone over 150,000 people crossed the bridge along with 1,800 vehicles (neither a small sum for the 1880s).

Unfortunately, a nasty rumor went around that the massive structure was unstable and doomed for collapse. Less than a week after the bridge was opened, a stampede of panicked citizens led to 12 casualties.

In order to quell public concerns about the safety of the bridge and, at the same time, bring a bit of attention to his circus, the famed showman P.T. Barnum marched his lead elephant Jumbo, along with a parade of all his other 21 elephants, over the bridge. The spectacle soothed the public and the rumor of the bridge’s instability vanished.

In reality, the rumor itself was always unfounded. Because the Brooklyn Bridge was designed long before the advent of modern bridge design and stress testing, the architect John Augustus Roebling over-engineered it in the grandest of fashions. In fact, the Brooklyn Bridge was so over-engineered that it was designed to be six-times stronger than it needed to be, just so Roebling could rest easy knowing that his creation would stand the test of time (and the load of hundreds of thousands of New Yorkers moving between Manhattan and Brooklyn).