Wikipedia
The Reichsautobahn system was the beginning of the German autobahns under the Third Reich. There had been previous plans for controlled-access highways in Germany under the Weimar Republic, and two had been built, but long-distance highways had not been successfully built. After previously opposing plans for a highway network, the Nazis embraced them after coming to power and presented the project as Hitler's own idea. They were termed "Adolf Hitler's roads" and presented as a major contribution to the reduction of unemployment. Other reasons for the project included: enabling Germans to explore and appreciate their country, and there was a strong aesthetic element to the execution of the project under the Third Reich; military applications, although to a lesser extent than has often been thought; a permanent monument to the Third Reich, often compared to the pyramids; and general promotion of motoring as a modernization that in itself had military applications.
Hitler performed the first ceremonial shoveling of dirt on September 23, 1933, at Frankfurt, and work officially began simultaneously at multiple sites throughout the Reich the following spring. The first finished stretch, between Frankfurt and Darmstadt, opened on May 19, 1935, and the first were completed on September 23, 1936. After the annexation of Austria, the planned network was expanded to include the Ostmark, and a second sod-breaking ceremony for the first Reichsautobahn on formerly Austrian territory took place near Salzburg on April 7, 1938. When work ceased in 1941 because of World War II, had been completed.