We report the first evidence of artificial ionospheric plasmas reaching sufficient density to sustain interaction with a high-power HF pump beam produced by the 3.6 MW High-Frequency Active Auroral Program (HAARP) transmitter in Gakona, Alaska. The HF-driven ionization process is initiated near the 2nd electron gyroharmonic at 220 km altitude in the ionospheric F region. Once the artificial plasma reaches sufficient density to support interaction with the transmitter beam it rapidly descends as an ionization wave to ∼150 km altitude. Although these initial artificial layers appear to be dynamic and highly structured, this new ability to produce significant artificial plasma in the upper atmosphere opens the door to a new regime in ionospheric radio wave propagation where transmitter-produced plasmas dominate over the natural ionospheric plasma and may eventually be employed as active components of communications, radar, and other systems.