In 1863 Zeppelin took leave to act as an observer for the Union's Army of the Potomac in the American Civil War in Virginia. Later, he travelled to the Upper Midwest with a party that probably included two Russians. Led by Native American (probably Ojibwe) guides, they canoed and portaged from the western end of Lake Superior up the St. Louis River and across to Crow Wing, Minnesota, on the Upper Mississippi River. On reaching St. Paul (via stagecoach and hired carriage), Zeppelin encountered German-born itinerant balloonist John Steiner and made his first aerial ascent with him from a site near the International Hotel in downtown St. Paul on 19 August. Many years later he attributed the beginning of his thinking about dirigible lighter-than-air craft to this experience.