  We describe the selection of the James Webb Space Telescope (JWST) North
Ecliptic Pole (NEP) Time-Domain Field (TDF), a ~14' diameter field located
within JWST's northern Continuous Viewing Zone (CVZ) and centered at (RA,
Dec)_J2000 = (17:22:47.896, +65:49:21.54). We demonstrate that this is the only
region in the sky where JWST can observe a clean (i.e., free of bright
foreground stars and with low Galactic foreground extinction) extragalactic
deep survey field of this size at arbitrary cadence or at arbitrary
orientation, and without a penalty in terms of a raised Zodiacal background.
This will crucially enable a wide range of new and exciting time-domain
science, including high redshift transient searches and monitoring (e.g., SNe),
variability studies from Active Galactic Nuclei (AGN) to brown dwarf
atmospheres, as well as proper motions of possibly extreme scattered Kuiper
Belt and Inner Oort Cloud Objects, and of nearby Galactic brown dwarfs,
low-mass stars, and ultracool white dwarfs. A JWST/NIRCam+NIRISS GTO program
will provide an initial 0.8--5.0micron spectrophotometric characterization to
m_AB ~ 28.8+/-0.3 mag of four orthogonal "spokes" within this field. The
multi-wavelength (radio through X-ray) context of the field is in hand
(ground-based near-UV--visible--near-IR), in progress (VLA 3GHz, VLBA 5GHz, HST
UV--visible, Chandra X-ray, IRAM30m 1.3 and 2mm), or scheduled (JCMT
850micron). We welcome and encourage ground- and space-based follow-up of the
initial GTO observations and ancillary data, to realize its potential as an
ideal JWST time-domain community field.
