Other cities in the 331 area code include: Lombard, Naperville, Elmhurst, Lemont, Geneva, Villa Park, Sugar Grove, Roselle, West Chicago, Barrington, Carol Stream, Warrenville, Plano, Aurora, Hanover Park, Hampshire, Yorkville, Bolingbrook, Pinckneyville, Glendale Heights, Montgomery, Big Rock, Itasca, Elburn, Streamwood, Kaneville, Maple Park, Glen Ellyn, Millbrook, Rolling Meadows, Woodridge, Elgin, and Wheaton.
Aurora, a suburb of Chicago, is a city predominantly in Kane County and DuPage County, with portions extending into Kendall and Will counties. It is located in the outer region of Greater Chicago in the U.S. state of Illinois. It is the second most populous city in the state, and the 114th most populous city in the country. The population was 197,899 at the 2010 census, and was estimated to have increased to 199,963 by July 2013. Once a mid-sized manufacturing city, Aurora has grown tremendously since the 1960s. Founded within Kane County, Aurora's city limits and population have since expanded into DuPage, Will, and Kendall counties.
Naperville is a city in DuPage and Will counties in the U.S. state of Illinois, and a suburb of Chicago. Naperville was voted the second-best place to live in the United States by Money magazine in 2006. It was rated 1st on the list of best cities for early retirement in 2013 by Kiplinger. In a 2010 study, Naperville was named the wealthiest city in the Midwest and eleventh in the nation with a population over 75,000. It was ranked among the nation's safest cities by USAToday and Business Insider. As of the 2010 census, the city had a population of 141,853, which was estimated to have increased to 147,100 by July 2015. It is the fifth-largest city in Illinois.
Chicago, officially the City of Chicago, is the third-most populous city in the United States. With over 2.7 million residents, it is the most populous city in the state of Illinois, and the Midwestern United States. It is the county seat of Cook County. The Chicago metropolitan area, often referred to as Chicagoland, has nearly 10 million people and is the third-largest in the U.S. Chicago is called the architecture capital of the United States. In terms of wealth and economy, Chicago is considered one of the most important business centers in the world. Chicago was incorporated as a city in 1837, near a portage between the Great Lakes and the Mississippi River watershed, and grew rapidly in the mid-nineteenth century.
The 331 area code lies within the Central Daylight Time Zone (or CDT). The current time in CDT is 0:06 AM on Jul 13, 2020.