* Library - Because it is a proper noun, referring to a specific place.
* Main - Because it is part of the proper noun "Main Street".
So the corrected sentence is: "You are going to the Library on Main Street."
* Library - Because it is a proper noun, referring to a specific place.
* Main - Because it is part of the proper noun "Main Street".
So the corrected sentence is: "You are going to the Library on Main Street."