reversing z-index based from page render order

Question

Example Markup:

<div class="wrapper">
    <h2>Trigger</h2>
    <div>This is some content</div>
</div>
<div class="wrapper">
    <h2>Trigger</h2>
    <div>This is some content</div>
</div>
<div class="wrapper">
    <h2>Trigger</h2>
    <div>This is some content</div>
</div> 

Example CSS:

.wrapper {z-index: 1}
.wrapper div {display: none; position: absolute;}

Via javascript (jQuery) I'm attaching a click event to each h2 that will then switch the content div to display: block.

The intent is that these are expandable blocks of content that will overlap anything else on the page.

The catch is that I'd like the first one to overlap the second, which would overlap the 3rd in the event that all of them are open.

However, since each one is being rendered AFTER the previous one, the actual stacking order is reversed (The last content div created end sup overlaying the previously created once).

Is there a clever way of reversing this behavior with CSS/HTML? Or is the solution to let the page render, then via javascript, grab all of the content divs in order and give them each a z-index in reverse order?

UPDATE:

Here's some more specific markup:

<div style="padding: 10px;">Hello World
    <div style="position: relative; top: -5px;">
        <div style="position: absolute; background: yellow;"><p>This</p><p>is</p><p>overlapping</p></div>
    </div>
</div>
<div style="padding: 10px;">Hello World
    <div style="position: relative; top: -5px;">
        <div style="position: absolute; background: orange;"><p>This</p><p>is</p><p>overlapping</p></div>
    </div>
</div>
<div style="padding: 10px;">Hello World
    <div style="position: relative; top: -5px;">
        <div style="position: absolute; background: red;"><p>This</p><p>is</p><p>overlapping</p></div>
    </div>
</div>

The following markup will produce 3 divs, each with a colored div overlapping. Due to the render order, the last absolutely positioned DIV (red) will be on top of the one before it (orange).

I can't figure out what type of z-indexes I need to apply to get the FIRST colored overlapping div to be on top. The order from top-to-bottom in terms of z-index should mirror the markup (yellow on top, red on bottom).

This is, of course, reverse of the standard.

I'm willing to use javascript to fix this post-display but I'm still struggling for the exact CSS that I need to apply via javascript. Is what I'm after doable?