maps_json

class WelcomeController < ApplicationController
  respond_to :html, :json

  def index
    @coordinates = {}
    @coordinates[:latitude] = 39.749813
    @coordinates[:longitude] = -104.999717
    # @coordinates = "#{latitude}, #{longitude}"
    respond_with @coordinates
  end
end

for the marker:

  // put jQuery or ajax
  $.get('welcome.json', function(welcomeData) {
      // welcomeData.forEach(function(welcome) {
      // make a new LatLng object
      var latlng = new google.maps.LatLng(welcomeData.latitude, welcomeData.longitude);
      // make a new Marker object
      var marker = new google.maps.Marker({
        position: latlng,
        map: map,
      // });
    });

      // place the marker on the map
      marker.setMap(map);
    });