St. Louis, Missouri, is famously known as the "Gateway to the West." This nickname originated during the westward expansion of the United States in the 19th century when the city served as a key starting point for pioneers heading into the western territories. The iconic Gateway Arch, built as a monument to this era, symbolizes the city's role in American history. St. Louis also has a vibrant cultural scene and rich historical significance that continues to attract visitors today. The confluence of the Mississippi and Missouri rivers further adds to its geographical importance in the narrative of westward migration.