<p>Fighting for labor rights in California's Central Valley, Dolores Clara Fernandez Huerta took up <em>la causa</em> in the name of children.</p>
<p>Muir struggled for decades to create and protect Yosemite National Park, and helped launch the American environmental movement.</p>
<p>In a momentous couple of years, the young United States added more than a million square miles of territory, including Texas and California. </p>
