Great horse manure crisis of 1894
The great horse manure crisis of 1894 is an urban myth that a significant obstacle to urban development at the turn of the 20th century was the difficulty of removing horse manure from the streets of major Western cities. The phrase originates from a 2004 article by Stephen Davies entitled "The Great Horse-Manure Crisis of 1894" which stated that "Writing in the Times of London in 1894, one writer estimated that in 50 years every street in London would be buried under nine feet of manure.".
Source: Wikipedia — Great horse manure crisis of 1894 (CC BY-SA 4.0)