The test was successful beyond the most optimistic expectations of anyone. ... There were tremendous blast effects. For a brief period there was a lighting effect within a radius of 20 miles equal to several suns in midday; a huge ball of fire was formed which lasted for several seconds. This ball mushroomed and rose to a height of over ten thousand feet before it dimmed. The light from the explosion was seen clearly at Albuquerque, Santa Fe, Silver City, El Paso and other points generally to about 180 miles away. ... A massive cloud was formed which surged and billowed upward with tremendous power, reaching the substratosphere at an elevation of 41,000 feet, 36,000 feet above the ground, in about five minutes ... Huge concentrations of highly radioactive materials resulted from the fission and were contained in this cloud. ... The cloud traveled to a great height first in the form of a ball, then mushroomed, then changed into a long trailing chimney-shaped column and finally was sent in several directions by the variable winds at the different elevations. It deposited its dust and radioactive materials over a wide area. It was followed and monitored by medical doctors and scientists with instruments to check its radioactive effects. While here and there the activity on the ground was fairly high, at no point did it reach a concentration which required evacuation of the population. Radioactive material in small quantities was located as much as 120 miles away. The measurements are being continued in order to have adequate data with which to protect the Government's interests in case of future claims. For a few hours I was none too comfortable about the situation.
-- Excerpts from General Groves' report to the Secretary of War after first atomic bomb detonation at Alamogordo Air Base, south-central N.M., July 1945. 
If you're riding trails and suddenly notice two dudes standing on the roof of a nearby building wearing plastic spacesuits, you might be in Los Alamos, New Mexico. Atomic City, U.S.A.
Just got back from a short trail tour of North-Central N.M. Despite a blanket of snow left in the high country, we were able to locate and roll vigorously upon several excellent trails near Santa Fe, Albuquerque and Los Alamos. There are really nice singletrack systems near all three communities   but the surprise of the trip was Los Alamos.
Los Alamos is an interesting little city with its post-nuclear micro-suburban developments laid out around several jagged canyons. The severe geography was a primary reason the site was chosen for the development of the first atomic bomb -- the canyons would provide safety and security for the facility, like a moat around a castle. Histories of the Manhattan Project tend to describe Los Alamos as a 'barren desert.' Such a misrepresentation will not survive in the age of the mountain bike. Down in those Ponderosa Pine-shaded canyons -- trails. Intense little trails with lots of interesting lines and challenges, the routes difficult to follow at times as they dip and dive and melt into the rock. On the canyon rims -- trails. Across the steep, fire-ravaged foothills above town -- trails. Los Alamos has an effective and hard-working group of trail stewards.
We rolled into town without the slightest clue and decided to hustle to the Caballo Bike Shop to get some direction. Our hustling turned into a fruitless search for the shop, but we called Joel, the owner-operator-mechanic, and he gave us detailed directions to find his tiny enclave behind the grocery store. Joel does a bit of retail -- say you need a water bottle or a gel pack, tube or tire -- but he's primarily engaged in service and repair. He was cleaning up a Santa Cruz when we walked in, told him we were from out of town and looking for some dirt. He confirmed that the taller trails would be wiped out by snow, but gave us directions to all the accessible stuff, and told us how to start a long ride from a trailhead that was just a few blocks away. He even closed up his shop to walk with us down to the grocery store to show us where to pick up a free trail map and discuss current events for thirty minutes. Joel was such a good host that I would like to give him some advertising: If you go to Los Alamos, go see Joel at Caballo Bike & Ski at 935 Central Avenue.
In my opinion, it would be a shame if Los Alamos became an overly-popular mountain bike destination a la Moab or Fruita. At least, until I've had a chance to ride there several more times. And if that did happen, it certainly wouldn't be the worst thing ever to have happened to Los Alamos.
Please be ultra-considerate and friendly to any hikers you see on these trails. This is your duty as a mountain biker.
 The entire memo can be found at the Nat'l Archives or in Sherwin, A World Destroyed, Appendices, pp. 308-14. Reading about the successful test of S-1 can be a bit creepy, but realize that literally hundreds of nuclear warheads have been exploded in the New Mexico and Nevada deserts since then.
 Santa Fe's Dale Ball system contains 20-30 miles of curvy, dusty, fast trails.
 At Cedro Peak east of Albuquerque there is an ungodly net of trails and doubletracks that stretches impressively, if not intimidatingly, into the great beyond. When lost in this system navigation is sketchy and involves frequent gazing through the junipers and across the bluffs in hopes of locating the radio tower on the modest hill that is Cedro Peak. Marking turns or leaving a trail of breadcrumbs would be of help to someone trying to find their way out. Some of the surfaces are a bit ripped up from ATVs but most of the trails are fun and there is plenty of volume available to string together a long, exhausting adventure.