Wright Field in Dayton, Ohio got the captured German material and went right to work.
"Shortly after arriving at Wright Field on August 10, 1946, and reporting to the Biophysics Branch, Special Projects Section, Captain Stapp was informed that he was now a project engineer assigned to the pilot escape technology program. He protested, making it clear that he was a doctor, not an engineer. The gruff branch chief, Colonel Edward J. Kendricks, explained that the unit was attached to the Engineering Division and immediately issued his new engineer a 1,200 page set of captured German technical documents, reports mostly, relating to aircraft ejection seat tests and biomedical examinations of human tolerance to the forces an explosive ejection creates. Kendricks had learned from Stapp's file that he was fluent in German."
[During the war] "The Germans had created elaborate test facilities at Tempelhof Airport in Berlin and had constructed a 60 foot ejection test tower." From p.p. 52 and 53 of Sonic Wind by Craig Ryan.
Wright Field's Technical Intelligence section [T-2] had 6 captured examples of the Heinkel He 219. Three are untraced, but the remainder had USA numbers. These were aircraft found by the British and transferred to the Americans by previous agreement. These received FE or Foreign Equipment numbers. USA 8 became FE-612, USA 9 to FE-613 and USA 10 to FE-614. The British acquired 7 examples. Czechoslovakia had 2 under the designation LB-79. Source: War Prizes by Phil Butler.