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We present a sample of 1165 extreme emission-line galaxies (EELGs) at 4<z<9selected using James Webb Space Telescope (JWST) NIRCam photometry in theCosmic Evolution Early Release Science (CEERS) program. We use a simple methodto photometrically identify EELGs with Hb + [OIII] (combined) or Ha emission ofobserved-frame equivalent width EW >5000 AA. JWST/NIRSpec spectroscopicobservations of a subset (34) of the photometrically selected EELGs validateour selection method: all spectroscopically observed EELGs confirm ourphotometric identification of extreme emission, including some cases where theSED-derived photometric redshifts are incorrect. We find that the medium-bandF410M filter in CEERS is particularly efficient at identifying EELGs, both interms of including emission lines in the filter and in correctly identifyingthe continuum between Hb + [OIII] and Ha in the neighboring broad-band filters.We present examples of EELGs that could be incorrectly classified at ultra-highredshift (z>12) as a result of extreme Hb + [OIII] emission blended across thereddest photometric filters. We compare the EELGs to the broader (sub-extreme)galaxy population in the same redshift range and find that they are consistentwith being the bluer, high equivalent width tail of a broader population ofemission-line galaxies. The highest-EW EELGs tend to have more compactemission-line sizes than continuum sizes, suggesting that active galacticnuclei are responsible for at least some of the most extreme EELGs.Photometrically inferred emission-line ratios are consistent with ISMconditions with high ionization and moderately low metallicity, consistent withprevious spectroscopic studies.

A Census from JWST of Extreme Emission Line Galaxies Spanning the Epoch of Reionization in CEERS