The 1890 Organic Act reassigned the Signal Corps' civilian weather duties to a new Weather Bureau under Agriculture, leaving the Signal Corps intact as a military body

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The statute that accomplished the 1890–91 transfer (claim-1890-91-weather-service-transferred-to-agriculture-at-harrisons-request) was the Act of October 1, 1890 (ch. 1266, §1, 26 Stat. 653), effective July 1, 1891. Per the U.S. Code's own editorial note, the Act "created the present Bureau in the Department of Agriculture"; before it, "the functions of the Weather Bureau were exercised by the Signal Corps of the Army." The Act's own operative text, as reproduced in Bob Glahn's NOAA-published institutional history, specifies the mechanism precisely: "the civilian duties now performed by the Signal Corps of the Army shall hereafter devolve upon a bureau to be known as the Weather Bureau... and the Signal Corps of the Army shall remain a part of the military establishment under the direction of the Secretary of War."

This distinguishes the transfer's mechanism from its fact: the Act split meteorology cleanly out of the Army as a defined set of "civilian duties," rather than dissolving or demoting the Signal Corps, which continued as a military body. The bill, S. 1454, was introduced in the Senate on December 18, 1889, by Senator William B. Bate of Tennessee "to increase the efficiency of the Signal Corps by transfer of the weather service to the Department of Agriculture" — framed, at introduction, as a Signal Corps efficiency measure rather than a rebuke of it. Army Chief Signal Officer Adolphus Greely, whose own tenure running the Bureau ended with this transfer (claim-greely-arctic-disaster-survivor-ran-us-weather-bureau-1887-1891), "did not strongly oppose the loss of the meteorological portion of the Signal Corps."