Are political signs allowed?

Political signs are permitted during the campaign period.

Why are political signs allowed?

Political signs are protected under the first amendment 

What is the first amendment? 

First Amendment

First Amendment Annotated

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press, or the right of the people peaceably to assemble and to petition the Government for a redress of grievances.