When the Long Branch is open, it has swinging doors for people to come and go through, as do most saloons. And when it is closed for the night, it has two solid doors that close and lock with a key. However, the solid doors are not there during the day when the swinging doors are, and the swinging doors are not there at night. In later episodes, this was changed so that, when the Long Branch is open, the solid doors are opened all the way and kept virtually flush against the walls.
The sign on Ma Smalley's boarding house, changes from one episode to the next. Sometimes it's on the porch railing, sometimes on the wall of the house, and sometimes on the roof.
Matt is called a US Marshal. Kansas became a state in 1861, more than a decade before the series is set. There was only one US district court in Kansas and one marshal assigned to it, plus a number of deputy marshal. All deputies would be based in Hays, the capital, not towns like Dodge. And deputies would enforce federal laws and court orders, and capture federal fugitives. They would not have state or local jurisdiction (like breaking up fights in the Long Branch). At the time of the series Dodge had a town marshal, and a county sheriff with jurisdiction outside the town limits.
The series is supposed to be set in the mid to late 1870's. Often people arrive in town in stagecoaches. However, when the Santa Fe Railroad arrived in 1872, all stage lines serving Dodge city either went out of business or dropped the city as a destination.
The Long Branch uses a pressurized beer delivery system (as evidenced by the beer taps), a system that was not invented until the early twentieth century.
The back linen on the first several of the seasonal dvds, state that Chester is the deputy. Contrary to popular belief, he never was.
The Long Branch- even though it has an open door- never seems to have any flies in it, although the smell of beer would attract them. In addition, the tables in the saloon seem to be stain free- even though they do not have tablecloths or any other protection from spilled drinks.
Almost all of the gun-toting characters wear the "buscadero" style combination belt-holster rig (low hanging for quick draw). The buscadero style was not invented until the early 20th century, either for Texas Rangers or for Hollywood cowboys. In the time period of "Gunsmoke," they would have worn holsters directly on their belts (as a very few characters do).
Most of the social, racial and political attitudes expressed by the characters during the series reflect the 1950s thru 1970s airing of the series rather than its 1870s/1880s setting.
The real Dodge City is located on green, rolling plains in SW Kansas. The setting of the series is instead in a semi-arid, hilly/mountainous area.