Checkboxes - Toggle Map Layers On And Off

We're using a JavaScript with Google Maps to load geographic data files and define parameters in Google's API. I have a working script that just needs one small change. The checkboxes toggle map layers on and off. Right now, only the last layer in the list is checked on load. We want all layers to be checked (and therefore displayed) on load.

Here's the [URL]

And here's my script:
<script type="text/javascript">
var map;
var userAdded = 1;
var layers = {
"Bones":
{"url": "[URL]",
"name": "Stream & Wetland Mitigation", .....

Here's some related HTML for display:
<input type="hidden" id="url" value=""/>
<div id="map" style="width: 870px; height: 800px; float:left; border: 1px solid black;"></div>
<div id="sidebar" style="float:left; overflow-vertical:scroll; height: 800px; width:150px; border:1px solid black">
<table id="sidebarTABLE">
<tbody id="sidebarTBODY">