I have a spatial file of the congressional districts of the US, however, the states are numbered in an unknown form. I have searched through all the other files but have found no key or description of the numbering of the states. Am I missing something? Here is the link where I downloaded the files.enter link description here
Based on comments, it seems your data is labeled with two-digit FIPS state codes. (FIPS stands for Federal Information Processing Standard.)
Here you can download a table with state names and FIPS codes, in this format:
FIPS State Code | Official United States Postal Service (USPS) Code | Name | Geographic Names Information System Identifier (GNISID)
You can join this table to the shapefile based on the FIPS code in your GIS software. A "join" or "table join" is a standard GIS process, it should be explained in the manual for your GIS software, as well as in many online tutorials. If you have any trouble, head over to GIS Stack Exchange.
Note: US localities have 5-digit FIPS codes. https://en.wikipedia.org/wiki/FIPS_county_code