Factual error: When Anton Sigurh stopped to refuel at the gas station in the middle of nowhere and the owner told him, "I seen you was from Dallas," that's a factual error. In Texas, the DMV issues license plate numbers at random, so that the man couldn't "read" Sigurh's tags to determine where the vehicle had been registered. Therefore, the very tense scene that follows, where the poor man is one coin toss away from getting killed, is based on a factual error.
Factual error: When Chigurh is in the gas station and throws the wrapper on the counter, the "Nutrition Facts" are visible on the label. Set in 1980, the "Nutrition Facts" label wouldn't have been available for at least another fourteen years, as nutrition labels were started in 1994.
Factual error: When Chigurh is in the gas station talking to the clerk, behind him on the shelf is a pack of Jack Link's beef jerky. The movie is set in 1980, but Jack Link's did not start selling beef jerky until 1986.
Factual error: At the very end of the movie, right before Javier Bardem is in the car accident, there is a shot out the driver's side window, past his face. In one of the driveways he is passing, a new Subaru Forester sits parked. The film is set in 1980.
Factual error: At the motel where Brolin's character first hides the money in an air vent, and when the hitman arrives to look for him, a silver 1985-1990 era Dodge Aries is parked prominently in the parking lot, despite the film's events taking place in 1980. (00:45:20)
Factual error: Despite the film's events taking place in 1980, several scenes feature a much newer 1986-1990 series Chevy Caprice (evidenced by the flush-mounted tail lights). The most obvious example is in the very first scene showing the rear of such a police car. (00:02:00)
Factual error: The glass milk jar in the Moss trailer that various characters drink from is labeled Promised Land Dairy. Although the movie is set in and around 1980, Promised Land Dairy didn't start producing milk products until around 1990 (http://www.promisedlanddairy.com/web-content/Our%20History.html).
Factual error: When Moss tells the border guard "I've got an overcoat on", a 1982+ Pontiac Grand Prix approaches behind him, though the film is set in June 1980. (01:27:50)
Factual error: When Josh Brolin is leaning against the guard wall outside the motel, there is a Carl's Jr. visible in the background. Carl's Jr. did not open stores in Texas until several years after the movie is set.
Factual error: In the desert "drug deal gone bad" scene, the red Ford Bronco has a blue oval in the grill. Ford did not start using blue ovals in the F-series until 1981. The movie was set in early 1980, per Agnes' tombstone, and 1981-model production didn't begin until August 1980. Further, the truck shown is modified, battered and rusty - certainly aged and well-used.
Factual error: As Sheriff Ed Tom Bell is driving up to The Desert Sands Motel, which is supposed to be located in El Paso, Texas, there is a sign on the right hand side which says "Route 66" - advertising a business on site. Route 66 did not go through El Paso - it was a few hundred miles to the north.
Factual error: In the opening monologue, Sheriff Bell remarks that at one point his father was the sheriff in Plano, Texas. However, the seat of Collin County, in which Plano is located, is actually McKinney.
Factual error: In the gas station, the snickers logo is the one they started using in 2005.
Factual error: The international bridge was in 1980 staffed by US Customs agents who wore blue uniforms. The agent questioning Brolin's character is wearing Border Patrol green.
Factual error: The satchel isn't large enough to hold $2 million. Maybe $1 million. There were six stacks showing on top, so $60,000 across the top layer. Each stack is nearly an inch deep, meaning that the satchel would have to have been about 30 inches deep, in other words 2 and 1/2 feet deep.
Factual error: When Josh Brolin is leaning on the cinder block fence at the motel towards the end of the film, behind him are some mountains and a tall building. The scene is set in El Paso, Texas but the mountains shown are the Sandia Mountains which are east of Albuquerque, New Mexico.
Factual error: The phone bill shows several calls from Area Code 210 (San Antonio). This Area Code did not exist until 1992, some 12 years after the movie is set.
Factual error: Carla Jean says she works at the Walmart in Sanderson, Texas. There is no Walmart there, nor has there ever been. The nearest one is 65 miles away in Fort Stockton.
Answer: "Blood Trail (end titles)" By Carter Burwell, the Coen's frequent composer. The Film does not have a soundtrack, but you can listen to it in Carter Burwell's website: http://www.carterburwell.com/projects/NCFOM.html.