Philadelphia
Philadelphia is the largest city in Pennsylvania, the second largest city in the northeastern United States, and the fifth largest city in the United States. The city lies in the northeastern United States according to the Delaware and Siquirky rivers, and is the only city and county union in Pennsylvania. According to the 2010 Census, the population of the city was 1,526,006 and increased to 1,547,607 in the 2012 census. Philadelphia is the economic and cultural center of the Delaware Valley, and the metropolitan area of the county is the sixth largest metropolitan area in the United States with a population of over six million. Within the Delaware Valley, the Philadelphia metropolitan area is divided into five districts and has a population of 4,008,994. The famous nickname of Philadelphia is the city of Philly and fraternity, which means the name of the city in Greek. "brotherly love" is a compound word of philos "loving" and adelphos "brother".