Question

During a snow storm, (Main street/Main Street) is always plowed first.

Answer 1

Answer:

During a snow storm, Main Street is always plowed first.

Explanation:

Main and Street are both part of a name

as "main" could be a adjective to the noun "street"  as well, another similar sentence could be

During a snow storm, the main street is always plowed first.

(The main street could have the name Bob's Alley)

Here, as neither "main" nor "street" are part of a name, no capitals required.