http://www.motherjones.com/politics/2014/07/child-migrant-ellis-island-history
The Immigration Act of 1907 did indeed declare that unaccompanied children under 16 were not permitted to enter in the normal fashion. But it didn't send them packing, either. Instead, the act set up a system in which unaccompanied children—many of whom were orphans—were kept in detention awaiting a special inquiry with immigration inspectors to determine their fate. At these hearings, local missionaries, synagogues, immigrant aid societies, and private citizens would often step in and offer to take guardianship of the child.
Other children journeyed to Ellis Island alone because they had lost their parents, often to war or famine, and had been sponsored by immigrant aid societies and other charities in America.
And of course, many of those kids grew up to work tough jobs, start new businesses and create new jobs, and pass significant amounts of wealth down to some of the very folks clamoring to "send 'em back" today.
Watch: Massachusetts Gov. Deval Patrick's Emotional Speech on Child Migrants
"This good nation is great when we open our doors and our hearts to aiding children and diminished when we don't"