Why did old-time armories have a half-barrel shape?

An armory originally was a place to store arms, and could be any old building. Many pre-1900 armories look like fortresses, as in the Army of the First Corps of Cadets in Boston.

Beginning about 1900, however, a larger, distinct, half-barrel style of armory became very common. Examples:

University of Illinois Armory
Minneapolis Armory
General Jones Armory in Chicago
Mission Armory in San Francisco

Because of their huge interiors, many of these armories later doubled as sports arenas. The University of Illinois ran indoor track in their armory for many years, and the Minneapolis Armory was once home to the Minneapolis Lakers.

Why the unique half-barrel style? And why only during that time period?

WAG. The more modern armories took into account vehicles. Having larger open spans allows trucks to maneuver inside without accidentally hitting building supports. If you’re looking to maximize open area in a building arches are the default construction method. I guess they could have added on cost and squared off the outside.

Probably copying the style of the famous Park Ave Armory which predates all of those (1880).

I’m guessing now, but maybe around 1900 was the time when artillery rounds became powerful enough so that the old fortress design wasn’t any use in turning aside shells.

Were they influenced by late-nineteenth-century train sheds?

The Park Avenue Armory(NYC) was definately influence by European train stations. It was the first of that design. The unit which used it was comprised of mostly affluent gentlemen and the design reflected that.

We are talking about armories built in the middle of cities. They were designed to be meeting and training locations for the gentlemen of the militia. There was no thought of it being a fortification.

Places that store explosives usually have sturdy walls and a tin roof to minimize damage when something goes boom.

The old “fortress” style Armory in my hometown had a large open area on the inside, which hosted basketball games as well as drill for the local militia/National Guard company until they built a bigger gym into the new high school in the 1920s. At the end of its life its interior was subdivided into a small shopping center, but when they tore it down, you could clearly see that most of the building was air despite the formidable-looking facade on the front.

Dammit is this thing on? Those armories where never design to store explosives. That is called a magazine. Armories then, as now, are where militia(now national guard units) go to drill. That’s it.

It seems to be a fairly standard design for buildings designed to have a large unobstructed floor space, like aircraft hangars (example, more examples). The arch-shaped cross-section gives it good strength without need for internal pillars. And because it’s linear in one dimension, construction is simple (it’s a repetition of the same shape).

I recently read that most of the armories in the US were built in reaction to the labor unrest of the late 19th C, after the Pullman Strike and Haymarket bombing. If the vaulted roofs have any connection to that purpose, I could only guess.

Your timeline is off. Aircraft hangers came later.

Here is a documentary about the Park Ave Armorydone for PBS.

The Park Ave Armory was the only privately funded armory in America. The 7th Regiment was comprised of the New York City gentry. They funded and built the armory. They used the best architects and designers of the time. The front part of the building looks like some of the fort-like armories (none of those were designed as actual forts). The vast drill floor was the rear of the building. It was done purposely to look like train sheds of the era and before including the original Grand Central Depot. It was the first building of its kind. The building was completed in 1880. Other armories built in the next few decades were built under government contract. They could not afford fancy architects like Charles Clinton and Sanford White. They “borrowed” from the previous design in New York.

Obviously. I didn’t say armory designs are based on aircraft hangars. I just said it’s a very common and logical design for maximizing clear (unobstructed) floor space.

Given the long list of riots and periods of civil unrest in the period from 1870 to 1910 or so, as well as the memories of the recent unpleasantness, it’s hard for me to be certain that the armories were not designed to be fortifications as well as training facilities. This one from 1895 certainly appears to be influenced by defensive strategies.

Logical but not easy. Prior to the Park Ave Armory most had columns on the inside of the open space. After it other buildings used for the same function copied the design. Aircraft hangers came later.

The term “armory” has varied meaning depending on location and era. It is not correct to say that they were only used for training. Historically they contained both arms and ammunition. (The hot stuff being stored in a special area within the armory.)

Being used as a large training area is a fairly recent National Guard thing. Link:

You would be incorrect. It was common for those buildings to have a castle-like facade. Many bear a resemblance to the Engineer Corps crest. I have been in quite a few of these old armories of various styles. None of them were built for defense. They are just buildings. The facades are just to give them a military look. During that time period armories were used for social gatherings. There was not much financial incentive to be in those units. They were men’s clubs.

The Park Ave Armory has a castle-like front side. The Lexington Ave side has the hanger shaped drill hall. It wouldn’t make sense to make half a castle if all you had to do was go around the block.

Side note: one of the old armories I worked out of had a very nice unique tile floor in the old office section. On the border it pattern contained a swastika every third character. I’m glad no one in the 40s overreacted and ripped it up.

Yes words can have multiple meanings. There was a Springfield Armory and a Harper’s Ferry Armory. They were places where arms were manufactured and stored. That is not the same as National Guard armories. where units trained and drilled. And met for dances and cigars. I can’t find where the first militia or National Guard building was that was called an armory was. But I have been specifically talking about those buildings built after the Civil War. Many were built between 1880 and 1900 especially in the north east. A big boom in Armory building occurred after 1916 when the NG was reorganized under federal law.

I think “inspired by” is probably correct, but if it were really built with defensive capabilities in minave so many windows so close to the ground.