Springs on Cahaba Mountain to the northwest form a fragile stream that grows as it carves through the steep, rocky terrain of Birmingham suburbs, then flows south across the Gulf Coastal Plain to the Alabama River at Cahawba, the site of Alabama's first capital. The Cahaba has sustained human life for at least 10,000 years and remains a major source of drinking water. Known nationally for its biological diversity and beauty, it is Alabama's longest free flowing river at 191 miles, nurturing 69 rare, imperiled aquatic species and the largest stand of shoals lilies on Earth.