The Niagara River, which connects Lake Erie and Lake Ontario, created Niagara Falls 12,000 years ago. The falls are where the Niagara River bends north 90 degrees.
Canadian Horseshoe Falls, American Falls, and Bridal Veil Falls make up Niagara Falls. Horseshoe Falls stands out. Niagara Falls became a tourist attraction in the 17th century.
Dickens wrote of his 1842 visit. "When I sensed how close to my Father I was standing, the immediate impression, and the enduring one—instant lasting—of the great scene, was Peace," he wrote.
Visitors leapt in the falls for ages. Among other oddities, a hotel owner sent a ship of animals over the falls, killing all save a goose.
The water changed on June 12, 1969. American Falls were switched off after 12,000 years. When 45 million gallons of water fell 11 storeys per minute, there was just a trickle.
To dam Niagara River, the US Army Corps of Engineers threw 27,000 tons of rock upstream. The aim was to spend six months examining if the boulders at the bottom of the falls could be removed.
The boulder pile near the waterfall had grown for years. That occurred quickly in 1931 and 1954, when 76,000 and 185,000 tons of rock dropped to the base, respectively.
The rocks were unattractive, and officials worried they might turn the falls into rapids if left.
The New York Times reported "grisly enthusiasm" when two remains were uncovered the day after the falls were halted.
Almost 100,000 people visited the waterless falls on June 1. That was quadruple last year's weekend attendance.
Engineers evaluated the boulder bed for five months before determining in 1974 that the boulders were needed to support the falls.