The seat of West-Central Ohio's Montgomery County, Dayton is located at the junction of the Stillwater and Great Miami Rivers approximately 50 miles north of Cincinnati . Prone to floods early in its history, markings on downtown lightposts clearly show the 1913 flood level well above the heads of passersby. Dayton is often cited as the 'Birthplace of Aviation' because it was here that Orville and Wilbur Wright began developing the first airplanes to be flown at Kitty Hawk, North Carolina. The massive Wright-Patterson Air Force Base is located just outside the city limits to the northeast. During the post-World War II period, the city developed one of America's highest concentrations of automobile and automobile-related manufacturing plants outside of Detroit, but that has changed in recent years. Dayton maintains active sister city relationships with Sarajevo , Bosnia-Herzegovina, Augsburg , Germany, Holon , Israel, Oiso, Japan, and Monrovia , Liberia.