 Starting 1918, all noncitizens started being required to obtain visas prior to entry to the United States, and in 1924, Congress enacted a provision requiring consular officers to make a determination of admissibility prior to issuing a visa.As a result, starting around this time, the majority of noncitizens coming to the United States for study did so on student visas.In the 1993 World Trade Center bombing, a truck bomb was detonated below the North Tower of the World Trade Center in New York City.