When Pierre L'Enfant drew up a plan for a city 10-miles square and centered on the Congress House (Capitol), there were no plans past the Washington monument in the mall area. In fact, the area where the Lincoln Memorial stands was the Potomic River.
In 1901 Senator James McMillan of Michigan organized the Senate Park Commission, later known as the McMillan Commission, to undertake a new plan for the Mall. The McMillan Plan extended the Mall by filling the river to form the sites for the future Lincoln Memorial and Jefferson Memorial. I am pretty sure permitting this fill was not a concern.
McMillan Commission Plan (Notice the pool was conceived as a cross)
The Lincoln Memorial was sited by the McMillan Commission and designed by architect Henry Bacon. Construction for the memorial began in 1914, but it did not open to the public until 1922. The Reflecting Pool was also designed by Bacon and was constructed after the Lincoln memorial was built between 1922 and 1923.
The pool is 2,029 feet long, 167 feet wide, and is about 18 inches deep on the sides and 30 inches deep in the middle. It holds approximately 6,750,000 gallons of water. Material excavated for the pool was used to landscape around the Lincoln Memorial.
So how did they waterproof the pool? The bottom was covered in cinders, followed by alternate layers of asphalt and tar paper. A final layer of slate was then laid on top. North Carolina Mt. Airy granite was used for the sides.
Ice skating on the pool was very popular when it first opened. It was reported on Feb 19, 1923, that by midafternoon there were 500 skaters enjoying the pool. People enjoyed skating in the park so much that there was some consideration in 1920s t0 add pipes and chillers to ensure the pool could be used all wintertime for skating. This idea was abandoned, however, after the price was reported to be $500k.
Notice anything strange in the next picture? Temporary buildings were erected during World War I and World War II to the north and south of the Reflecting Pool. Two wooden walkways were built over the pool during World War II. After some protest, these walkways were removed after the war in 1947.
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