The federal government has some 13,200 minors in custody, mostly older children and teens who travel to the border alone in the hopes of meeting up with parents or other close relatives already living in the U.S. The average time spent at one of the shelters is 48 days, according to the Department of Health and Human Services.
"The internment of Japanese Americans is a stain on our history," Sanders, I-Vermont, a 2020 presidential candidate, tweeted. It's "abhorrent that 75 years later, this administration now wants to hold migrant children in one of those same camps."
"We will look back on Trump’s racist child prisons as an abomination," he added.
Sanders' Senate office did not immediately respond to a request for comment on whether he opposed the program when it was under Obama. The tweet was sent from his senator account on Twitter, not his presidential campaign handle.
Sanders, an independent, was never in lockstep with Obama’s handling of undocumented migrants, saying in 2016 he would end the “deportation regime” he said was created by the president. ABC News could not immediately find instances where Sanders spoke out against using the base when the Obama administration placed minors there.
Republican lawmakers from Oklahoma issued a joint statement in support of the move to place children at the base.
"While the announced use of Fort Sill as a shelter for these children is only temporary, it certainly highlights the dire need for a permanent solution to manage the border crisis," said Oklahoma GOP Rep. Tom Cole, whose district includes Fort Sill.
Sen. Jim Inhofe, R-Oklahoma, who spoke out against Obama’s use of Fort Sill in 2014 said he now supports using the base under Trump. He accused Obama of having created the crisis at the southern border, although the numbers of undocumented migrants declined sharply before Obama left office and have spiked dramatically in recent months amid Trump's threats to close the border.
In addition to Oklahoma, Obama used installations in Texas and California for 7,000 unaccompanied migrant children after other shelters hit capacity.
In 2014, Inhofe said in a statement: “Our nation has an immigration problem and a national security crisis, but I don't believe the answer is for our military facilities to be transformed into a center that houses, feeds, and cares for illegal immigrants.”
Included in the crush of 144,000 migrants in the month of May alone were some 11,000 undocumented kids traveling without their parents, classified by the government as "unaccompanied alien children." Upon arrival, the children are supposed to be transported to a shelter within 72 hours. But capacity levels in recent days has topped 90% and officials at the Department of Health and Human Services say the shelters with open beds didn't always match the child's needs.
As a result, some 2,000 kids at one point were waiting at border stations to move on to the more than 100 privately run shelters scattered around the country. HHS says it needs Congress to approve $2.9 billion in emergency funding soon or else it will be unable to pay the shelters.
Democrats have criticized the facilities, which are often not subject to state child welfare licensing requirements because they are temporary emergency shelters. One such shelter, tent-like facilities in Tornillo, Texas, shuttered amid political pressure and protests. Many of those kids were shuttled to Homestead, Florida, where thousands of teens are living until they can be placed with sponsors. Advocacy groups said they are planning to protest at Homestead on Sunday.
“Detention traumatizes young people and tears apart families and communities," Mariana Martinez, an organizer with the American Friends Service Committee and a resident of Homestead.
Government officials say, however, they need time to ensure the child is processed and placed in a safe situation.
ABC producer Mariam Khan contributed to this story.