Peggy takes a sample of Steve's blood, explaining that she wants to see how his "genetic code" has been altered. But no one in 1942 would have spoken of a "genetic code": James Watson and Francis Crick did not even discover the DNA molecule until 1953, and it was at least another decade before its coding sequence was well understood. However SHIELD has advanced technology and knowledge at their disposal, so it isn't unlikely that they would have this knowledge, even if it was not known to the public at the time.
When Captain America is doing the bond promotion, there is a scene where a motorcycle drops from above (on cables) with three people on it. The engine in the motorcycle shows it to be a post-1985 "Evolution" engine.
Steve Rogers is shown wearing a screen-printed t-shirt. Prior to WW2, t-shirts were blank and used as underwear. Soldiers popularized wearing the plain t-shirts as standalone shirts, and printed ones began to appear in the 1950s.
When Steve Rogers and Carter are sat in a bombed out pub in London during an air raid, a rather modern sounding two tone emergency services vehicle siren can be heard outside. Emergency vehicles during the 1940s used bells and this type of siren was not used until the 1970s.
Before Captain America and Bucky zip line onto the Hydra train, Jim Morita can be seen wearing a H4855 Personal Role Radio, an item which only came into use in 2002, for the British Army. While they do have advanced equipment it is unlikely they'd have something 50-60 years before it was actually in use. Especially as Captain America's team is not the British Army.
Red Skull is heard listening to a recording of Richard Wagner's opera "Die Walkure" ("The Valkyrie") in an early scene with Dr Zola, but the recording he is listening to, conducted by Herbert von Karajan and featuring the distinctive voice of Canadian tenor Jon Vickers, wasn't recorded until 1968. 25 years after the scene takes place. What's more, the same record contains both Siegmund's aria "Ein Schwert verhieß mir der Vater" from "Die Walküre" and Siegfried's funeral march from "Götterdämmerung," heard without a break. Both pieces could not have fitted on one side of the short-playing 78 records used during World War II.
When Steve Rogers and Dr. Erskine are sitting in the barracks having a discussion, Steve's footlocker has his social security number on the lid. During World War II, military personnel had a service number which had a different format than the social security number used by today's military.
A number of the tracked vehicles seen outside the German prison are the FV432 armoured personnel carriers. These vehicles are part of the British fv430 series of armoured vehicles which have been mistaken for the similar American M113 armoured personnel carrier. Both vehicles were first in service in the 1960's 17 years after the time frame in which the film is set.
When a German grenade is used a 'ping' of the striker handle being released from a 'Pineapple' style grenade is heard. The German stick grenade is ignited with a pulled cord which starts a chemical friction ignition.
When Steve Rogers arrives at the building for his transformation, he exits the car and puts on his hat prior to entering the building. He then wears the hat indoors until the procedure starts. Military personnel are required to remove their headgear while indoors unless they are armed (such as Military Police).
The Union Flag hanging outside the War rooms is upside down. At the flagstaff, the white Saltire of St. Andrew (Scotland) takes precedence over the red Cross of St. Patrick (Ireland) because Scotland has been part of the Union longer than Ireland, i.e. at the flagstaff the white diagonal band must be thicker above the red diagonal. While many countries fly their flag upside down in times of war, the United Kingdom is not one of them.
The icon used for Hydra looks like an octopus with a skull instead of a head, with many arms. A hydra, on the other hand, has many heads emanating from a single trunk-body, not many arms as an octopus does.
During the radio broadcast of the Dodgers-Phillies game, the broadcaster mispronounces the name of Brooklyn outfielder Pete Reiser as "riser", but it should be "reeser". The broadcaster is apparently Red Barber, the Dodgers' long-time announcer, who would have known how to pronounce Reiser's name.
When Steve is crawling under the barbed-wire in boot camp, Hodge kicks one of the posts loose and causes the wire to fall on him. The sergeant yells at him, "Rodgers, get that rifle out of the mud," but it's Hodge's rifle that was in the mud, and Steve clearly keeps his barrel off the ground.
Dr. Erskine says he is from Queens, NY, 73 St. and Utopia Pkwy. This is incorrect as both streets run North-South and are about 5 miles apart. The correct Street is 73 Ave. which does cross Utopia Pkwy.
After Schmidt reveals his true face in the Hydra base to Captain America, the two begin their first fight scene. It's here that Red Skull displays his super strength and punches Captain America's steel shield leaving a fist impression in the metal. The two keep fighting but the fist impression is no longer on the shield. Later at HQ, when Stark pats the shield and remarks how Rogers is attached to it, the punch impression is there again.
The railing on Captain America's side in the 1st Hydra base (after Bucky crosses the gap on the bar) is intact, but when Rogers decides to jump, the railing is broken for no reason, and he bends one end away.
When Captain America's ice-encased shield is revealed in the beginning of the movie, the paint job is pristine with no damage. However, in the final fight with the Red Skull, the shield is seen to have numerous dings and scores in the paint from bullet strikes.
When Steve Rogers and Dr. Erskine are sitting in the barracks, Dr. Erskine pours a drink for each. Dr. Erskine is at first gripping the bottle around its neck. In the next cut, he is holding the bottle further down around the wider part of the bottle.
A map shows the allied positions close to the Italian/Austrian Border. By 1943 when the film is set, they hadn't even taken Rome yet, which fell in June 1944. They would not even come close to the border until November 1944.
The map behind Col. Phillips at the last briefing depicts modern-day Canada, all in the same color. Newfoundland and Labrador didn't join Canada until 1949; before then, it was an separate Dominion ruled directly from London.
Captain Steve Rogers wears the yellow American Defense Service ribbon. The ribbon/medal was awarded for qualifying service performed between September 8, 1939, and December 7, 1941. Since Rogers joined the Army after America's entry into WWII, he would not be entitled to wear this ribbon.
During WW2 if a soldier/sailor/marine did not come back from a mission, he was initially declared "Missing in Action" (MIA). Only later would he be listed as "Killed in Action" (KIA). Sometimes this occurred long after WW2 ended.
The role of the fake Adolf Hitler Captain America pretends to punch at the end of his live appearances is misspelled in the end credits as "Adolph Hitler". The correct spelling has always been with an "f" instead of "ph".
The old lady in the antique shop, among other characters, uses a Thompson model sub-machine gun (M-1928) that held a 20 round magazine. The entire weapon was normally emptied in less than 4 seconds of continuous fire, making the shoot-out in the antique store impossible without several pauses to reload.
On the train, Captain America's sidekick fires a Colt 45 M1911 until it is empty, visibly locking the slide back. He attempts to fire it again, but it goes click. This type of pistol doesn't do that, because the hammer can't move when the slide is back.
In the scene where Steve and the Sgt are going to Brooklyn and the secret lab he is not wearing his garrison hat in the car. When he gets out of the car he does not put it on. He walks all the way to the doorway of the fake store and as he enters, he puts the hat on. This is not in keeping with military custom. He should have had the hat on before he got out of the car, and should have taken the hat off as he entered the store.
Some have taken issue with the ribbon placement on Col. Phillips uniform; specifically the placement of the Silver Star. The placement is correct as the order of precedence ranks it below the Distinguished Service Medal (Army). Others have taken exception to the placement of the Combat Infantry Badge on the pocket flap - while this is technically the incorrect placement it was a common occurrence with paratroopers in WWII who placed their Airborne insignia on top.
Military units show African-Americans and appear to be integrated, but the troops were not integrated until 1948. However this is a specialty unit from a fictitious military branch, not a standard battalion.
When Rogers is becoming Captain America he initially has a strap across his chest prior to the super soldier serum being injected, when he emerges from the machine at the end of the scene the strap is no longer there. The strap is off because Rogers was growing to his new size/height and was becoming stronger due to the Vita-rays and Super-Soldier formula, so the strap likely snapped off during the experiment.
Some have taken issue when Captain America is presented with his second shield, he is told that it is vibration-proof. Instead he is told that it is "totally vibration absorbent" therefore absorbing the vibration of incoming projectiles and not even allowing them to ricochet.
While chewing out Agent Carter for helping Rogers on his mission to free Bucky Barnes and other captured soldiers, Colonel Phillips leaves the tent without a helmet on. The next scene cuts to him walking outside his tent with a helmet on. While it's easy to miss, the Colonel grabs his helmet on the way out of the tent. He simply put it on as he walked.
The exposition depicted in the movie is not, as some viewers have assumed, the World's Fair in New York City, which happened in 1939, much too early for the film. The characters actually attend the fictional "Modern Marvels of Tomorrow" exposition.
The Nazi soldiers appear to perform an improper salute (two-handed, and mispronouncing "Hitler.") However, if one is paying attention, they are clearly saying "Hail HYDRA", and are thus apparently performing a HYDRA-specific salute, with a different motion than the well-known one-handed Nazi salute.
When Steve Rogers pulls Heinz out of his little submarine boat and throws him onto the dock - then climbing a ladder out of the water himself - both characters are dry. Their clothes are dry and no water is dripping on the ground beneath them.
Stark accidentally detonates an ammo pellet taken from one of the Red Skull's weapons while examining it in a safety chamber. Although the observation window explodes in Stark's face with enough force to blow him across the room, the only injury he suffers is a small cut over his right eyebrow.