The period  between the civil war and the 1st world war was a prosper period during which the whole nation passed from a rural country to an urban state. The civil war stimulated the technological progress which at its turn stimulated the economic life. During the post civil war many technological achievements have  been reached as the perfection of the electrical telegraphy by Samuel F.B. Morse in 1844, the invention of the telephone by Alexander Graham Bell in 1876, and so inventions flooded.
The most important industrial section was steel  production, in Agriculture too the revolution was great.

         The American  was moved by an imperial urge chased the Spanish from Cuba, Puerto Rico and the Philippines  in 1898, Cuba remained under American control till its independence in 1934.  Same thing for the island to Puerto Rico it was and still very related to the United States.  Moreover, its  people have the American citizenship. 
In 1914 the American Government, which has a perpetual lease on the stripe of land in Panama which  relates  the Atlantic ocean to the Pacific ocean, dug the Panama canal.
In 1959 Hawaii became the 50th state in the union.
The United States, 2had purchased Alaska from the Russians in 1867, maintained that the whole coastline was U.S. territory

           On October 1917 the United States of America  declared war to the German under Wilson's mandate, for the German submarines sunk 5 U.S. vessels, it is the 1st world war. 

          n March 1941 the U.S. Congress passed the Lend-Lease Act and appropriated an initial $7 billion to lend or lease weapons and other aid to any countries the president might designate. By this means the U.S. hoped to ensure victory over the Axis without involving its own troops. By late summer of 1941, however, the U.S. was in a state of undeclared war with Germany. In July, U.S. Marines were stationed in Iceland, which had been occupied by the British in May 1940, and thereafter the U.S. Navy took over the task of escorting convoys in the waters west of Iceland. In September President Franklin D. Roosevelt authorized ships on convoy duty to attack Axis war vessels. The war ended with the dropping  of a nuclear bombe on Japan on 1945.
In the post world wars period the United States lived a troubled relationship with the ex-Soviet government, those troubles were known as the could war which ended by the dismantlement of the Soviet Union.  On of the most marked events related to the cold war was the Vietnam War.
In August 1962 John H. Glenn Jr.  became the first American Astronaut to orbit the earth, In July 1969 under the Apollo Project  Neil A. Armstrong became the first human to land on the moon.
Long after  the civil war blacks suffered from discrimination till the 1960s, the civil right's spokesman was Martin Luther King Jr. During the following years the Civil Right Act in 1964 and the Voting Right Act of 1965.
          In 1991 the U.S.A was engaged in the war for the liberation of the Kuwait from the Iraqi Invasion, the war was called the Gulf War. America wanted to preserve its economic interests in the Middle East region related to the oil supply. 
In the last decades, The United States of America reached a strong  economic, social, political and technological development which gave the country an outstanding advantage against all the other countries.