How to Return Text with IF Function in an Array

First time poster. Thanks for all the great help!

In Google Sheets, I'm trying to query a column and look for a state abbreviation, and if that abbreviation is a match, then "East" if not then "West"

Wanting to return text values in my column based on state abbreviation. We have territory manager split into two domains--East and West. So, trying to easily sort my data by East/West.

Here's what I have:

=IF(M:M={"AL", "CA", "DE","FL","GA","IA","KY","ME","MD","MA","MN","MS","NH","NJ","NY","ND","RI","SD","TN","VT","VA","WV","WI"},"East","West")

But, when I fill down, it just fills down East, and does not seem to actually query M:M

Thoughts?

Thanks so much!