How are the racing categories in the US decided? I have heard mention before of racing cyclists in the US being, say, a Category 2 racer.  What are these categories and how are they decided?
Usually, it is the USA Cycling racing categories that people are referring to. 


Road Upgrades
Guidelines and Notes by Category:


5-4:   Experience in 10 mass start races.
         Local Associations may also establish policies where upgrade
         credit is given for taking asanctioned rider education clinic.

4-3:   20 points; or experience in 25 races with
        a minimum of 10 top ten finishes with
        fields of 30 riders or more, or 20
        pack finishes with fields over 50. 30
        points in 12 months is an automatic upgrade
        - USA Cycling-sanctioned rider camps and clinics that are
          approved by the Local Associations for upgrading will
          count as a maximum of three upgrade points when upgrading
          from category 4 to 3

3-2:   30 points
         40 points in 12 months is an automatic upgrade

2-1:   35 points
         50 points in 12 months is an automatic upgrade