  The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator
for the Galactic Center's black hole Sagittarius A*. Here we present the first
total and linearly polarized intensity images of this source obtained with the
unprecedented 20 $\mu$as resolution of the EHT. J1924-2914 is a very compact
flat-spectrum radio source with strong optical variability and polarization. In
April 2017 the source was observed quasi-simultaneously with the EHT (April
5-11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline
Array (April 28), giving a novel view of the source at four observing
frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties
from the subparsec to 100-parsec scales. We combine the multi-frequency images
of J1924-2914 to study the source morphology. We find that the jet exhibits a
characteristic bending, with a gradual clockwise rotation of the jet projected
position angle of about 90 degrees between 2.3 and 230 GHz. Linearly polarized
intensity images of J1924-2914 with the extremely fine resolution of the EHT
provide evidence for ordered toroidal magnetic fields in the blazar compact
core.
