It's Saint Louis, Missouri. Although whoever did it didn't get it right. The blue lines are supposed to be curved, representing the rivers.
"The design submitted by Professor Emeritus Theodore Sizer, Pursuivant of Arms at Yale university, and now on file in the office of the City register is approved, adopted and designated as the official flag of the City. The flag with a solid red background has two broad heraldic wavy bars, colored blue and white, extending from the left top and bottom corners toward left center where they join and continue as one to the center right edge. This symbolizes the confluence of the Missouri and Mississippi rivers. Over the point of confluence a round golden disk upon which is the fleur-de-lis of France (blue) calling attention to the French background of the early city and more particularly to St. Louis of France for whom the City is named. The golden disk represents the City and/or the Louisiana Purchase.