With the declaration of war, Amateur Radio in the United States was shut down for the duration. Both transmitting and receiving were banned, and amateurs were required to take down their antennas.
The official order was printed in QST, May 1917:
DEPARTMENT OF COMMERCE
Office of Radio Inspectoor
To all Radio Experimenters,
By virtue of the authority given the President of the United States by an act of Congress, approved August 13, 1912, entitled “An Act to Regulate Radio Communication,” and of all other authority vested in him, and in pursuance of an order issued by the President of the United States, I hereby direct the immediate closing of all stations for radio communications, both transmitting and receiving, owned or operated by you. In order to fully carry this order into effect, I direct that the antennae and all aerial wires be immediately lowered to the ground, and that all radio apparatus both for transmitting and receiving be disconnected from both the antennae and ground circuits and that it otherwise be rendered inoperative both for transmitting and receiving any radio messages or signals, and that it so remain until this order is revoked. Immediate compliance with this order is insisted upon and will be strictly enforced. Please report on the enclosed blank your compliance with this order, a failure to return such blank promptly will lead to a rigid investigation.
Lieutenant, U.S. Navy,
District Communication Superintendent