Asymmetrical Spindle installation
 

I'm in the middle of installing this square taper SR BB and suddenly started doubting myself on which side the longer end of the spindle goes to. The crank side, correct?

Yup. Most times anyway.

It's generally the right side that needs the extra room for chainring/chainstay clearance, so long side to the right. If the left needed more room, or the right didn't it would have been symmetrical.

You should be able to read the ingraving on the axle from the top of the bike.

...facing forward.

As all of the above posters said, the vast majority of the time the longer end is installed toward the drive side and you shoud be able to read the engraving properly while seated on the bike and looking through a "transparent" bottom bracket shell.

That said, I did run into an exception years ago. I had a '93 Trek 7000 MTB that came with a Tange cup-and-cone bb and a Deore LX 110/74 triple crank. When I first overhauled it I discovered the bb spindle had been installed with the long end toward the non-drive-side. After muttering some uncomplimentary things about the factory incompetence, I proceeded to install it the "right" way only to have the non-drive side crank arm hit the chainstay! Apparently the fat chainstays on this frame required an extra long spindle and reverse installation to clear everything properly.

Same thing happened to me overhauling a BB on a customer's bike of similar vintage. That's why my original answer said "most times".