Maine has more than 70 lighthouses along over 3,400 miles of rugged shoreline winding past craggy cliffs and cobble beaches. Built on rocky promontories and offshore islands, these lighthouses have warned mariners of navigational hazards and guided them home since the 1800s. In that era, the waters were busy with ships carrying granite, lumber, and fish to distant ports and returning goods to Maine. Today, the lights serve lobster boats, sailing schooners, tour boats, and cruise ships. Each lighthouse has a unique light pattern and color that lets mariners identify its location by its light's fingerprint. Bass Harbor Head Light was built in 1858, automated in 1974, and shows a red light that occults every four seconds. Its original fifth order Fresnel lens was replaced in 1902 with a larger fourth order lens.