Throughout the history of the United States there has been a constantly fluctuating relationship between the United States and Mexico. Because they share borders, it is natural for the United States and Mexico to have a flow of individuals going in and out of the respective nations. Traditionally, throughout history, this has always been an occurrence.
During the largely formative years of the United States, throughout a good portion of the 1900s, Mexico was having issues regarding their land and the availability of work,. At this time,the United States had programs established to bring Mexican immigrant workers up to help them with ranches and labor-intensive work.
Throughout the nations there were Mexican immigrants found working as mechanics, painters, plumbers and various other jobs that were required. Furthermore, the Mexican immigrants were required to obtain contracts if they desired to leave the workforce of the United States, in order to go back to Mexico. The reason for such necessity for Mexican immigrant workers was due, in part, to World War I. During World War I, a good portion of American men were sent out to serve; this left all vocational fields open, and factory jobs were also required in order to make goods for the troops.
Throughout the war years, the Mexican immigrant worker numbers grew to the millions. However, along with this grew tension between the United States and Mexico. After World War II had ended, a large portion of Mexican Immigrants who came to the United States for work during war years were returned to their homeland. Since them, the issue of Mexican Immigration has become a more sensitive overall. Issue of illegal immigrants and border control problems have lead several upsurges of tension between the nations.