MMR here stands for Minimum Maintenance Road, but in healthcare, MMR is short for Measles-Mumps-Rubella vaccine. Here's a couple fast facts about the second "M" in MMR, mumps:
The salivary glands swell due to illness caused by mumps.
Hippocrates first described mumps in the 5th century BC. He gave the description about the symptoms, which include face and throat swelling. A mumps epidemic was quite widespread in the 18th and 19th century, breaking out all around the world, including the military, prisons, boarding schools and ships at sea.
Mumps vaccine was approved for use by the FDA in the year 1967. The combination vaccine, MMR was invented in the year 1971, and came into use in public in 1977.
As for the cache: This is probably the hardest of the three in the series to obtain. The location of this cache will test your ability to enhance your z-axis. No special tools are required. But, you'll need some determination and perseverence to claim this find. There is just a log, so bring a writing utensil. Please maintain the integrity of the cache's location and the area around gz.
There are parking coords listed for this cache. I ask that you please use them. The local residents won't have the time or inclination to help retrieve your vehicle from this road/goat path, should you become stuck.
Practice CITO where appropriate. Take your time. Try not to overstretch your physical abilities, and above all, have fun while cursing iowaPete's name out loud!