The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a balloon-borne cryogenic telescope a measure cosmic star formation history at redshifts up to z=3.5. EXCLAIM will shed light on the mysterious peak in cosmic star formation rate around z ~ 2, and its subsequent decline despite the continued growth of dark matter halo masses. EXCLAIM will utilize the line intensity mapping technique, detecting emission from carbon monoxide (2.5 < z < 3.5) and a ladder of emission lines from singly-ionized carbon (0 < z < .9). Line intensity mapping detects the cumulative emission from many galaxies simultaneously, resulting in a CMB-like map of brightness fluctuations at each redshift. This results in an unbiased census of the underlying emission lines that is simple and economical to extend to large volumes. EXCLAIM will utilize cooled optics at ~1.5 K and will feature a 90 cm primary mirror. The optics will be coupled to an array of microfabricated silicon integrated spectrometers with aluminum microwave kinetic inductance detectors (MKIDs), which will be read out in a frequency multiplexed system relying on BLAST-TNG heritage. The spectrometer-detector system will be cooled to 100 mK, allowing the detectors to operate well below the superconducting transition temperature of aluminum. The cooled optics and low background emission in the upper atmosphere present a highly sensitive testing environment for MKID performance, demonstrating the detectors’ potential for use in future missions including space-based telescopes. EXCLAIM is slotted for a summer 2021 engineering flight and a summer 2022 science flight.