Monroe County, Illinois in the context of "St. Louis Metropolitan Statistical Area"

Greater St. Louis is the 23rd-largest metropolitan statistical area (MSA) in the United States consisting with an MSA population more than 2.8 million, and almost 3 million CSA the largest in Missouri, and the second-largest in Illinois. Its core city—St. Louis, Missouri—sits in the geographic center of the metro area, on the west bank of the Mississippi River. The river bisects the metro area geographically between Illinois and Missouri, although the latter portion is much more populous. The MSA includes St. Louis County, which is independent of the City of St. Louis; their two populations are generally tabulated separately.

The St. Louis, MO-IL metropolitan statistical area (MSA) includes the City of St. Louis; the Illinois counties of Bond, Calhoun, Clinton, Jersey, Macoupin, Madison, Monroe, and St. Clair (known collectively as the Metro East); and the Missouri counties of Crawford (only the City of Sullivan), Franklin, Jefferson, Lincoln, St. Charles, St. Louis (separate from and not inclusive of the city of St. Louis), and Warren.

St. Philippe is a former village in Monroe County, Illinois, United States. The settlement was founded in ca. 1723 by Frenchman, Philip Francois Renault, during the French colonial period. St. Philippe was strategically located near the bluffs that flank the east side of the Mississippi River in the vast Illinois floodplain known as the "American Bottom". The village was located three miles north of Fort de Chartres. Because of many decades of severe seasonal flooding, St. Philippe and the fort were both abandoned before 1765. After the British takeover of this area following their victory in the Seven Years War, many French from the Illinois country moved west to Ste. Genevieve, Saint Louis, and Missouri

Waterloo is a city in and county seat of Monroe County, Illinois, United States. The population was 11,013 at the 2020 census, up from 9,811 in 2010.