Area 51 got it's name from the Nevada Test Site's Area 51 (you may say duh). The Nevada Test Site has had many radiation releases over the years. The DOE has a document containing information about these releases, which can be found here. You can look up information based on the "test name". I've summarized the major releases in the table below:
| Test Name | Max Gamma Exposure (mR/h) | Location |
| SEDAN | 1960 | Queen City Summit |
| SCHOONER | 350 | On highway 25 (now the ET Highway) near the Lincoln-Nye county line |
| DES MOINES | 160 | Queen City Summit |
| TRAVELER | 65 | Clark Station |
| PLATTE | 47 | Queen City Summit |
| BANDICOOT | 20 | highway 95, 7 miles west of the Mercury junction |
| SMALL BOY | 14 | 13 miles south of Alamo |
| ANTLER | 12.5 | Twin Springs Ranch (near Basecamp) |
| EEL | 10 | 5.9 miles northwest of Queen City Summit |
| BUGGY | 8.5 | 4 miles east of Warm Springs |
| PIN STRIPE | 8 | 18 miles northeast of Groom Lake |
| PIKE | 5.9 | Cactus Springs (just north of Indian Springs) |
| JOHNNIE BOY | 3.8 | Twin Springs Ranch (near Basecamp) |
| DANNY BOY | 3.2 | 17.7 miles west of Warm Springs |
| PALANQUINN | 3 | Stone Cabin Ranch (about 14 miles west of Warm Springs) |
| PAMPAS | 0.22 | Penoyer |
| PARROT | 0.14 | along highway 25 (now the ET Highway) |
To put this in perspective, a good chuck of unprocessed uranium would read in the 15 to 20 mR/hr range (combined beta and gamma). Nuclear workers are allowed 5 rems per year whole body exposure. [Homer Simpson, being a cartoon character, has no such limit.] Taking the Sedan test release, you would be allowed to hang around Queen City Summit for about 2.5 hours before your dose for the year was reached. www.atomicrocks.com has a good reference on dosimetry here.
The information for the top two releases follows:
The radiation levels around the Nevada Test Site are monitored continuously, and can be read online in near real time. This is through the Department of Energy Community Environmental Monitoring Program (CEMP) These monitoring stations can be seen on the CEMP website. Typically areas around the Nevada Test Site have gamma radiation levels around 10 to 20 uR/hr. Note the table above is in mR/h, or a factor of 1000 higher.
Queen City Summit has obviously taken its share of nuclear releases. However, it has a natural radioactivity that has been augmented with fallout. A study on the radiation of Queen City Summit can be found here. To see a Real Player video of a geiger counter at Queen City Summit, click here. The scale multiplier is 0.1, and the geiger counter was set up to read both beta and gamma. The video isn't very sharp, but basically the meter is running from 50 to 70 uR/h.