Final answer:
Nearly 19 million immigrants arrived in the United States between 1890 and 1921 during the Progressive Era.
Explanation:
Between 1890 and 1921, almost 19 million immigrants arrived in the United States. This period, known as the Progressive Era, saw an influx of people from various countries such as Russia, Poland, Italy, and Mexico.
Learn more about Immigration history in the United States here:
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