Angular/UI-Router - How Can I Update The URL Without Refreshing Everything?

I'm new to both Angular and the ui-router. When someone selects a model and my controller performs a standard SHOW method, I simply want to update the URL to include the model's ID without refreshing the page, and continue on with my original view. I'm not sure how to do this...

$stateProvider
        .state('citylist', {
          url: "/",
          templateUrl: "views/index.html"
        })
        .state('cityshow', {
          url: "/city/:id",
          templateUrl: "views/index.html"
        })

angular.module('app.system').controller('IndexController', ['$scope', 'Global', 'Cities', '$stateParams', '$location', function ($scope, Cities, $stateParams, $location) {

    $scope.loadTown = function(id) {
        Cities.get({id: id }, function(city) {
             $scope.city = city
             // Change URL
             // Do things within the same view...
        });
    };
});

<button ng-click="loadTown(123456)">Chicago</button>