Jets, my understanding is that the Observatory retired as a commercial enterprise in 1923, and subsequently became a tourist attraction and viewing post. The old Portland Folk Club used to gather there for sings and for special events such as Halloween.
Here's some more Portland Observatory verses; there's lots more history than verses so far:
With his telescope in the lantern room, He'd scan the Bay around, And hoist a signal up the mast When a vessel there he found.(CHO)
'Twas in the War of 1812, He beheld a thrilling sight, As the Enterprise beat the Boxer, It was one brutal fight. (CHO)