And up the hill on vine street (The main black corridor) sat our carnegie library Mrs. Long always glad to see you The stereoscope always ready to show you faraway Places to dream about
As the poet moves along the streets of her past, she finally comes to the place: the Lawson McGhee Library.
She calls it the Carnegie Library because it was one of many libraries around the country founded by a grant of money from the ginormously wealthy Andrew Carnegie.
Up to this point, race hasn't really come into the poem. But Giovanni puts it front and center here by showing us that the neighborhood is predominantly a black one ("the main black corridor") and that she identifies herself very strongly with it ("our carnegie library").
It's important to note this detail now, because it will make lines 27-32 easier to understand (yes, we're predicting the future, but just trust us for now).
Mrs. Long also makes her first appearance here. It's interesting that we don't see a description of a kind face or a pretty dress or any physical detail like that.
For Giovanni, the most important thing about Mrs. Long is her welcoming attitude (a great attribute for a librarian, we think).
It's also telling that the library is the place where you find "faraway/ Places to dream about."
And it's not just the books that open a door into new worlds: it's a stereoscope. If you're not too old (or too young) to remember them, a View-Master is a child's version of the stereoscope.
Giovanni uses a very mild form of epistrophe in lines 24-25. Epistrophe uses the same word or similar phrase structures at the back end of a poetic line: "Mrs. Long always glad to see you/ The stereoscope always ready to show you."
It's a nifty verbal trick, but it also creates a gentle rhythm in a stanza that talks about the lovely, welcoming nature of Mrs. Long.