Abstract:  The use of highly energetic protons to treat deep seated tumors was envisioned by Robert Wilson in 1946. Due to their finite range and large energy deposition at the end of travel, energetic protons were recognized as having the potential to deposit less dose in healthy tissue for a given dose to a targeted tumor than their commonly used x-ray counterparts which deposit dose with a decaying exponential distribution. In the last half century proton radiation therapy has seen limited use, not due to its efficacy, but rather due to the very high cost and complexity of the accelerators required to generate protons of suitable energies. In 2000 Dr. Kenneth Gall conceived of a proton therapy system which would make use of the very high magnetic fields present in superconducting MRI systems in conjunction with an old fashioned accelerator technology, the variable frequency synchrocyclotron. The combination of these two critical pieces of technology enabled the construction of a very compact, simple, and cost effective proton therapy system. This presentation describes the underlying physics of proton radiation fields and describes the engineering development of this device including its many challenges and successes.