At Rest Under Pyramids

We stumbled upon the small national cemetery in St. Augustine today.  It's immaculate and well-kept and directly across the street from the water.

What was astounding is that there are three pyramids in it.  They are quite old, and made of the coquina substance.  When you read the plaque it says that 1,466 soldiers who died in the Indian Wars (1835-1843) are buried beneath them.

The cemetery grew around them.

It does not explain why the pyramids were chosen.  I did some reading, and basically there isn't an explaination.  I know a pyramid is on the dollar, but that was decided on in 1935 - many years later.

So what was the significance in utilizing these symbols in burying fallen soldiers of war?  A mystery.