National Park Service Boundaries

The National Park Service Boundaries dataset is consumed from an external ArcGIS web service via the following URL and ID

https://mapservices.nps.gov/arcgis/rest/services/LandResourcesDivisionTractAndBoundaryService/MapServer
ID: 2

OpenLayers

If you are developing in OpenLayers, you will want to use the OpenLayers ArcGIS93Rest class. An example of your solution might look similar to the code below.

layer = new OpenLayers.Layer.ArcGIS93Rest(
    "National Park Service Boundaries",
    "https://mapservices.nps.gov/arcgis/rest/services/LandResourcesDivisionTractAndBoundaryService/MapServer/export",
    {
        layers: "show:2",
        transparent: true
    },
    {
        isBaseLayer: false
    }
);
map.addLayer(layer);