Wyoming license plates have stacked numbers 1-23 on the far left that represent the 23 counties in the state. That means that residents can tell what part of the state a vehicle is from by looking at those numbers, something that everyone in Wyoming knows. License plates on the vehicles in the show start with "24", a non-existent county.
The scenes for Longmire's cabin are filmed in the Valles Caldera in the Jemez Mountains of New Mexico. The caldera is a 14-mile-wide volcanic crater. It is now a national preserve. Several Westerns including The Missing (2003) and The Lone Ranger (2013) have used this location.
Sheriff Walt Longmire (Robert Taylor) carries a 1911 .45ACP Colt Government Model with custom stag grips for his duty sidearm. Unlike most who choose to carry the M1911, he carries it in Condition 2 (mag inserted, round chambered, hammer down). This isn't necessarily a technical error; there was a time when this was the acceptable method of carry, although now most M1911 users do not recommend it for safety reasons, instead choosing Condition 1 (mag inserted, round chambered, hammer cocked, safety on) which is the way the pistol is designed to be carried.
Carrying his sidearm the way he does, round chambered and the hammer down, makes a lot of sense for two reasons. From a theatrical standpoint you get the effect of his cocking the hammer. It also agrees better with his character who "sometimes likes to think before he talks (acts)" by making discharging his weapon a more deliberate act.
While a guest on "Conan" (2010), Jeff Garlin promoted "Longmire" by showing a clip from the show, instead of plugging his own show The Goldbergs (2013). He explained, '''Goldberg' is a huge hit, No. 3 comedy on TV. 'Longmire' needs help. I love 'Longmire' and I want that show to keep going.''
The series takes place in Wyoming, but is filmed in and around Santa Fe and Las Vegas, NM. The sheriff's office is on the plaza in Las Vegas at 1811 Hot Springs Blvd., just across from the famous Plaza Hotel. Many scenes are also filmed in Pecos, NM, and in the Pecos Wilderness north of the town of Pecos. Filming is also done in Espanola, NM, at one of the casinos.
Walt's beer of choice is Rainier, named in honor of Washington's Mount Rainier. Longmire is the name of the historic district within the Mount Rainier National Park; it's named for David Longmire, who led a wagon train of travelers to the Tacoma area.
In the series pilot, the license plate on the sheriff's vehicle has "5" as the first number, indicating that the vehicle is from Albany County. That is where Laramie is located, along with the University of Wyoming, which is the only university in the state. Laramie is in southeastern Wyoming, bordering Colorado. The Snowy Range mountains are just west of the city. Interior shots are filmed at the Greer Garson Studios on the campus of the Santa Fe University of Art and Design, in Santa Fe, NM.
In the books (long before the TV show was cast), Longmire often imagines casting classic movie actor Robert Taylor to play himself. Coincidentally, in the TV series, a different (and arguably better) Robert Taylor was cast for the leading role.