In October of 1918, one month before the end of the war, the Radio Section moves into the new Radio Building (the last piece of available real estate on Connecticut Avenue).
WWV was born...but didn't broadcast "standard frequency ... calibrating frequency" until 1923. In the meantime, they did propagation tests, reception tests, tuning tests and pioneered the future of radio by broadcasting music.
In the Spring of 1920, they were broadcasting well known music on several frequencies and later that year ... using direct tube modulation (greatly improving fidelity). The telephone was still used to announce the selections!
Also in the Spring of 1920, by request of the Department of Agriculture, they started broadcasting Market Reports. Both of these proved very popular and soon were taken over by commercial broadcasters.