1990

Historically, Farm Tillage Tools Were Designed Without Scientific Knowledge Of How Tools Work The Soil. Thus, A Tool Designed To Operate In One Soil Pulled By A Mule Might Not Operate Satisfactorily In Another Soil Or When Pulled By A Tractor At Higher Speeds. Traction And Flotation Problems Appeared With The Introduction Of Tractors. The Importance Of Developing A Scientific Approach To The Study Of Tillage And Traction Became Apparent During The Transition From Animal To Mechanical Power.

The Rain Bird horizontal action impact drive sprinkler head was invented in 1933 by Orton Englehardt, a citrus grower and native of Glendora. The design offered slow rotation and uniform watering, benefits long sought by local irrigators. Clement M. LaFetra, a friend of Englehardt, urged early patent application. A patent was awarded on December 18, 1933. Englehardt, with no entrepreneurial aspirations, assigned all rights to LaFetra and his wife Mary Elizabeth. Production began in the LaFetra family barn on October 13, 1935.

Rapid development of aircraft design in the 1930s required many related innovations, including propeller design. The hydromatic propeller by Hamilton Standard marked a significant advance over the counterweight-type, controllable pitch propeller. The first test flight of the prototype took place in 1938: the public demonstration was made by a United Air Lines DC-3 over New York City on April 6, 1938. It played a distinguished role in allied combat aircraft in World War II.

The Salginatobel Bridge, spanning the Salgina Valley ravine, is the earliest surviving three-hinged, hollow box arch bridge designed by  Robert Maillart.

Built to cross one of the steepest valleys along the Douro River, the Ponte Maria Pia was the first major work to emerge from the French firm of Gustav Eiffel  and Company, establishing Eiffel as an important bridge designer and civil engineer of his day. Resting on a parabolic arch spanning 160 meters, the Ponte Maria Pia was the longest iron arch bridge in the world at the time of its construction. The bridge's latticework construction reflects the later design of the well-known Eiffel Tower, erected in Paris to commemorate the International Exposition of 1900. 

This was the first successful machine for mechanizing the identification and price marking of retail merchandise. At a single stroke of the operating handle, the machine formed a tag from a roll of stock, imprinted it with price and other information, formed a wire staple, and stapled the tag to the merchandise. This means for dispensing with handmade and written tags amounted to a minor revolution in the then rapidly expanding retail industry.

When the Adams Plant went into operation on August 26, 1895, it represented a key victory for alternating-current systems over direct-current. The clear advantage of high voltage AC for long distance power transmission and the unprecedented size of the plant (it reached its full capacity of ten 5,000-HP generators in May 1900) influenced the future of the electrical industry worldwide. In August 1895 the Adams No. 1 generating station of the Niagara Falls Power Company first supplied electric power to local industries in Niagara Falls, New York.

The Fort Peck Dam was a cornerstone project of the Works Progress Administration of Franklin D. Roosevelt's New Deal. It required the largest construction plant and workforce since the construction of the Panama Canal and peaked at 11,000 workers. It was the largest dam of any type in the world for over 30 years.

John Vincent Atanasoff conceived basic design principles for the first electronic-digital computer in the winter of 1937 and, assisted by his graduate student, Clifford E. Berry, constructed a prototype here in October 1939. It used binary numbers, direct logic for calculation, and a regenerative memory. It embodied concepts that would be central to the future development of computers.