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==Organization==
[[File:Feed Material Network.png|thumb|right|Feed Material Network - organization chart]]
[[File:Cumulative receipts of uranium oxide in ore by source for the Manhattan Project.png|thumb|A graph showing the cumulative receipts of uranium oxide in ore and concentrates for the Manhattan Project (1942-1947). Numbers are in tons of uranium oxide.]]
Initially, the firm of [[Stone & Webster]] made arrangements for the procurement of feed materials, but as the project grew in scope, it was decided to have that company concentrate on the design and construction of the [[Y-12 electromagnetic plant]], and arrangements for procurement and refining were handled by Marshall and Nichols.{{sfn|Manhattan District|1947a|pp=1.15–1.16}}
In October 1942, Marshall established a Materials Section in the Manhattan District headquarters under Lieutenant Colonel Thomas T. Crenshaw Jr., an architect. To assist him, he had [[Captain (United States O-3)|Captain]] Phillip L. Merritt, a geologist, and Captain John R. Ruhoff, a chemical engineer who, as St Louis Area engineer, had worked on uranium metal production.{{sfn|Jones|1985|p=307}}<ref>{{cite magazine |title=Thomas T. Crenshaw Jr. '31 |magazine=Princeton Alumni Weekly |date=4 December 2013 |url=https://paw.princeton.edu/memorial/thomas-t-crenshaw-jr-31 |access-date=20 February 2025}}</ref> When Ruhoff, a chemical engineer who worked for [[Mallinckrodt]], was inducted into the Army, Nichols had him assigned to the Manhattan District.{{sfn|Compton|1956|pp=95–96}} Crenshaw became the officer in charge of operations at the [[Clinton Engineer Works]] in [[Oak Ridge, Tennessee]], in July 1943, and was succeeded as head of the Materials Section by Ruhoff, who was promoted to lieutenant colonel.{{sfn|Manhattan District|1947a|pp=1.15–1.16}}{{sfn|Jones|1985|p=308}}
The following month, the Manhattan District's headquarters moved to Oak Ridge, but the Materials Section and its successors remained in New York until 1954.{{sfn|Jones|1985|p=308}}{{sfn|Harris|1962|p=30}} Nichols, who succeeded Marshall as district engineer on 13 August 1943,{{sfn|Nichols|1987|p=101}} felt that this was a better ___location for it, as it was close to the ports of entry and warehouses for the ores and the headquarters of several of the firms supplying feed materials. He reorganised the section as the Madison Square Area; engineer areas are normally named after their ___location, and the office was located near [[Madison Square]].{{sfn|Jones|1985|p=308}}
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