On January 15, 1919, a huge storage tank full of hot molasses exploded in the North End. Fifteen foot waves of the sticky sweetener flowed through the streets at 35 miles per hour. Twenty-one people died, 150 were injured, houses flattened and the area was flooded with three feet of standing molasses. The true cause of the rupture was never solved.
When Shari and I visited Boston, there was no evidence of molasses. It was kind of sticky getting out of town during rush hours though.