Kenai Peninsula, a peninsula in southern Alaska. It juts southwestward into the Pacific Ocean from just below Anchorage and is bordered by Cook Inlet, the Gulf of Alaska, and Prince William Sound. The Kenai is about 160 miles (260 km) long and up to 120 miles (190 km) wide. Much of the land is mountainous and heavily wooded. There are large icefields at high elevations; glaciers descend to the sea along parts of the east coast. Lumbering, fishing, and the production of petroleum are the chief economic activities. Seward is the southern terminus of the Alaska Railroad and the peninsula's largest city and chief port.