Answer: Aqueducts
Explanation: They were first developed around 312 B.C., these engineering marvels used gravity to transport water along with the stone, lead and concrete pipelines and into city centers. Aqueducts liberated Roman cities from reliance on nearby water supplies and proved priceless in promoting public health and sanitation.
As the Cold War unfolded in the decade and a half after World War II, the United States experienced phenomenal economic growth. The war brought the return of prosperity, and in the postwar period the United States consolidated its position as the world's richest country. Gross national product, a measure of all goods and services produced in the United States, jumped from about $200 thousand-million in 1940 to $300 thousand-million in 1950 to more than $500 thousand-million in 1960. More and more Americans now considered themselves part of the middle class.
The growth had different sources. The automobile industry was partially responsible, as the number of automobiles produced annually quadrupled between 1946 and 1955. A housing boom, stimulated in part by easily affordable mortgages for returning servicemen, fueled the expansion. The rise in defense spending as the Cold War escalated also played a part.
During the Civil War, the North had the advantage of having many officers with training and experience.
Answer: commander in chief
