The Chicago Air Shower Array (CASA) was a significant ultra high high-energy astrophysics experiment operating in the 1990s.

It consisted of a very large array of scintillation detectors located at Dugway Proving Grounds in Utah, USA, approximately 80 kilometers southwest of Salt Lake City.

CASA was built to study the possibility of astrophysical sources of ultra high energy (UHE, E > 100 TeV) gamma-ray emission (see Science below).

The plan for CASA was to build a much more sensitive experiment that would be much larger in size, use state-of-the-art electronics, and be coupled with a large array of muon detectors (MIA).

These experiments reported excess air shower events from the direction of two well-known Galactic X-ray binary sources: Cygnus X-3 and Hercules X-1.

After these results, a number of groups around the world began designing, or improving, air shower arrays to make follow-up studies.

Cronin's idea was to build a definitive experiment that could easily verify, or refute, the results on Cygnus X-3.

Construction activities were carried out at the University of Chicago in the Accelerator Building of the Enrico Fermi Institute.

The completed scintillation detectors, along with electronics, were shipped to Utah in large semi-trailers, where they were installed by students, postdocs and faculty.

The scientific results from CASA-MIA encompassed a dozen scientific publications and covered topics in three broad areas of high-energy astrophysics: gamma-ray point sources, diffuse gamma-ray sources, and cosmic ray physics.