Ohio (State of Ohio) is in the east-central part of the United States, near the Great Lakes. The land area is about 100,000 square kilometers and the population is about 11.53 million. The state's economy is more developed, with more agriculture and manufacturing. In terms of transportation, air transportation is extremely developed, and there is a transportation research center. Important airports are Cincinnati-Northern Kentucky International Airport (CVG), which is a transit center for Delta Air Lines, and Cleveland Hopkins International Airport (CLE), which is a transit center for Continental Airlines, and Toledo Airport (TOL), here is the US National Express Transit Center, so it is very convenient to send express and goods here. In addition, important airports are Port Columbus International Airport (CMH), Dayton International Airport (DAY), Youngston-Wynn Regional Airport (YNG). Ohio's abbreviated ZIP code is OH and the area code is: 216 - 234 - 330 - 419 - 440 - 513 - 614 - 740 - 937. The major cities are Columbus 43085-43299, Cleveland 44101-44199 and Cincinnati 45201-45999.