Ruby on Rails 3 model to serve US States without a database

State.rb

class State
  include ActiveModel::Conversion
  extend ActiveModel::Naming

  attr_reader :all

  US_STATES = {
      AL: "Alabama",
      AK: "Alaska",
      AZ: "Arizona",
      AR: "Arkansas",
      CA: "California",
      CO: "Colorado",
      CT: "Connecticut",
      DE: "Delaware",
      DC: "District of Columbia",
      FL: "Florida",
      GA: "Georgia",
      HI: "Hawaii",
      ID: "Idaho",
      IL: "Illinois",
      IN: "Indiana",
      IA: "Iowa",
      KS: "Kansas",
      KY: "Kentucky",
      LA: "Louisiana",
      ME: "Maine",
      MD: "Maryland",
      MA: "Massachusetts",
      MI: "Michigan",
      MN: "Minnesota",
      MS: "Mississippi",
      MO: "Missouri",
      MT: "Montana",
      NE: "Nebraska",
      NV: "Nevada",
      NH: "New Hampshire",
      NJ: "New Jersey",
      NM: "New Mexico",
      NY: "New York",
      NC: "North Carolina",
      ND: "North Dakota",
      OH: "Ohio",
      OK: "Oklahoma",
      OR: "Oregon",
      PA: "Pennsylvania",
      RI: "Rhode Island",
      SC: "South Carolina",
      SD: "South Dakota",
      TN: "Tennessee",
      TX: "Texas",
      UT: "Utah",
      VT: "Vermont",
      VA: "Virginia",
      WV: "Washington",
      WV: "West Virginia",
      WI: "Wisconsin",
      WY: "Wyoming"
  }

  SE_STATES = [ :AL, :FL, :GA, :KY, :MS, :NC, :SC, :TN, :VA ]

  # If we initialize the class, return a hash with all the states
  def initialize
    @all = US_STATES
  end

  def to_hash
    @all
  end

  def to_a
    @all.keys.sort
  end

  def to_s
    @all.values.sort.to_sentence
  end

  def persisted?
    false
  end

  # Class Methods
  class << self

    def all
      US_STATES
    end

    def southeast
      US_STATES.slice( *SE_STATES )
    end

    def method_missing(method_id, *arguments, &block)
      state     = method_id.to_s.titleize
      state_sym = method_id.to_s.upcase.to_sym
      if US_STATES.has_key?(state_sym)
        { state_sym => US_STATES[state_sym] }
      elsif US_STATES.has_value?(state)
        { US_STATES.key(state) => state }
      else
        super
      end
    end

    def respond_to?(method_id, include_private = false)
      if US_STATES.has_key?(method_id.to_s.upcase.to_sym) or US_STATES.has_value?(method_id.to_s.titleize)
        true
      else
        super
      end
    end

    alias_method :se, :southeast
    alias_method :SE, :southeast

  end
end

You can call the class methods directly to get hash slices, e.g:

State.all => Simply returns the entire US_STATES hash
State.southeast => Returns a hash of just the SouthEastern states (also aliased to State.se)
State.abbr or State.name => Returns a hash slice containing just the state requested ( i.e. State.nc or State.north_carolina => {:NC => "North Carolina"} )