No picture of said stairs? Come on...

Universal Hub & MassDOT answered this in 2016:

<https://www.universalhub.com/2016/all-longfellow-bridge-salt-and-pepper-shakers-back>

Last line of the (long) article:

Nothing; they’re empty. 

Just a clarification for anyone looking for the answer in this link, it comes about half way down in the comments, not in the main text of the post.

Salt, duh! For winter. Some bridges don't have salt shakers built in, and those bridges are dangerous when there's snow.

Salt and pepper.

It is a long article, especially for a quick question. But the article has you read the interesting history about the bridge and I think it’s a good way to draw people in.

Paprika obvi!

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I'd like to buy actual salt 'n pepper shakers that are copies of the Longfellow bridge towers.

They are Nike Missile silos

There's a diagram

I thought those were in the fells?

Thats what someone who knew a great treasure was hidden inside them would say.

Me

There was a set in the Blue Hills. After it was decommissioned people used to meet there with CB and Ham radios to swap equipment. That was before the MIT Flea.

Apparently the site in the fells was a different kind of anti-aircraft base, and was decommissioned when the nike missiles came out. Interesting article here: https://www.medfordhistorical.org/wp-content/uploads/2022/09/MHSNewsletterFall2022-LO.pdf

I suspect the confusion stems from people thinking we’re saying “salt and pepper bridge” with a Boston accent. Those towers contain exactly what they’re supposed to - that is to say they’re hollow, for acoustic amplification purposes, and they carry a reverberating rendition of “Push It!” every time a broken-down train is moved across the Salt-N-Pepa Bridge.

An untapped market opportunity.

Well, if you were around in 2013 you knew there was nothing inside as you watched them being disassembled and then rebuilt...