  We introduce Probing Radio Intensity at high-Z from Marion (PRIZM), a new
experiment designed to measure the globally averaged sky brightness, including
the expected redshifted 21 cm neutral hydrogen absorption feature arising from
the formation of the first stars. PRIZM consists of two dual-polarization
antennas operating at central frequencies of 70 and 100 MHz, and the experiment
is located on Marion Island in the sub-Antarctic. We describe the initial
design and configuration of the PRIZM instrument that was installed in 2017,
and we present preliminary data that demonstrate that Marion Island offers an
exceptionally clean observing environment, with essentially no visible
contamination within the FM band.
