Sources: Manhattan: Bolted at the Edge of the Grid

Books
Precise Leveling in New York City by Frederick W. Koop, Board of Estimate and Apportionment, New York, 1914.
Washington Heights Manhattan: Its Eventful Past by Reginald Pelham Bolton, Dyckman Institute, 1924.
The Measure of Manhattan by Marguerite Holloway, W.W. Norton & Company, Inc., New York, 2013.

Websites, accessed January 2017
"The Trinity Cemetery & Mausoleum," Trinity Wall Street.
"Web Exclusive: The Xs and Ys of the Big Apple," January 29, 2001, BNP Media.

Periodicals, accessed online January 2017
"Wigwam," The World: New York, 29 Oct 1872.
"Harlem" New York Press, 1889.
"Only Two Nominations," New York Times, 23 Oct 1889.
"Hungry for Office," New York Times, 16 May 1889.
"Minor Municipal Matters," New York Times, 3 May 1893.

"Who Moved the Body," The Syracuse Courier, 9 May 1895.

"On the Trail in Earnest," The Syracuse Courier,10 May 1895.
"Still a Mystery," Rochester Democrat and Chronicle, 12 May 1895.
"Culver was Crazy," New York Herald, 12 May 1895.
"A Detective at Work," The Syracuse Courier, 1 June 1895.

"Missing Roommate and Money," New York Herald 20 Dec 1897.
"Civil Service List," The Daily Standard Union, Brooklyn, 1897.
"Mr. Palmer's Application," Brooklyn Daily Eagle, 10 Feb 1899.
Brooklyn Daily Eagle, 7 Jan 1914.

Frederick W. Koop obituary, Brooklyn Daily Eagle, 18 Aug 1922.
Alston G. Culver obituary, New York Times, 25 Nov 1927.
"The Grid at 200," New York Times, 2 Jan 2012.