I've been wondering this myself as well.
Some would say "1st" cannot be a name as ordinal numbers aren't letters and "1st" should only be used as an Abbreviation. I would always have a ordinal number "1st" as an abbreviate name. For example the First New Hampshire Turnpike in Northwood NH I labeled the abbreviation as "1st NH Tpke"
Now on the Official name I think it is easy: How does the governement recognized the name. If it's "1st" use that if it's "First" use that.
On the Primary name generally I think the street sign is the best indicator of this as it represents what people are looking for. Or you could use the name most people use for the Address.
I think that if for some reason the full spelling of the ordinal number isn't present it should be there, if not just as an Obscure number so it doesn't evade search.
Just putting out my general thought but wonder what others think.
Date: Fri, 22 Feb 2013 09:46:08 -0800 (PST)
Subject: name entry for roads with ordinal numbers
Okay, so the most common street name in the United States and Canada is Second Street / 2nd Street. This is a name with an
ordinal number. I actually see nothing in the guidelines on how to deal with street names with ordinal numbers (but guidelines do deal with numbered highways, which is a different subject).
Am I right that all street names with such ordinal numbers should only be input as 1st, 2nd, 3rd, etc. and not First, Second, Third, etc. even as an additional name because they would automatically be parsed and converted internally anyways when searching using the spelled out version? What happens if a community exclusively uses the spelled out name for First through at least Ninth on street signs, rather than 1st through 9th? Or how about cities that use both like in San Francisco, such as these for Third Street / 3rd Street:
http://goo.gl/maps/rJLi9 http://goo.gl/maps/9uTZ5 and
http://goo.gl/maps/kGuoT
Many style guides, in dealing with street names, say to spell out First through Ninth and leave 10th and above using numerals and letter suffixes. How should we deal with that here on Google Map Maker? What about international variants?