As many as 700,000 migrants, a foreign population larger than Boston, Massachusetts, are currently in Mexico waiting to rush the United States-Mexico border when President Joe Biden ends the public health authority known as Title 42 on May 11. In 2020, in the midst of the Chinese coronavirus crisis, former President Donald Trump invoked the public health authority known as Title 42 at the border, ensuring that federal immigration officials have been able to quickly return millions of illegal aliens to Mexico over the last three years.