The National Institutes of Health is shuttering its chimpanzee research program after decades of experimentation and research that has put animal rights activists and scientists at odds.

Two years after sending more than 300 of its research champs into retirement, the NIH said on Wednesday that it will place the final 50 chimps into sanctuary. The move puts an end to government-led experiments on chimpanzees, the primate most closely related to humans. Chimp DNA is nearly 99 percent identical to human DNA.

"It's time to say we've reached the point in the U.S. where invasive research on chimpanzees is no longer something that makes sense," Dr. Francis Collins, director of NIH, told the Associated Press.

The news was heralded by animal rights groups. “We really see the [NIH] closing and locking the door behind the chimps and throwing away the key on their way out of the laboratories,” Wayne Pacelle, president and CEO of The Humane Society of the United States, wrote in a blog post.

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The NIH first established primate research facilities in 1960. But in the past few years, under increasing outside pressure, the agency had scaled back its work. In 2013, the NIH retired all but 50 chimps, hanging on to them in case they were needed for some essential research.

But in the past nearly three years, not a single request for research on a chimp has been made. “[W]e have moved on from the time when research on chimpanzees was considered essential," Collins told the journal Nature.

Wednesday’s news did not come without some backlash. Some scientists working on a vaccine to protect chimps in the wild from the Ebola virus decried the decision. Others wondered if some future health crisis would be worsened without chimps available for testing.

The final decision by the NIH was not made without some arm-twisting and years of bureaucratic machinations. The NIH asked the Institute of Medicine (now the National Academy of Medicine) to look at the need for chimp research back in 2010, and the IOM came back with a report in 2011 that determined most of it was unnecessary. That led to the retirement of hundreds of chimps in 2013.

Then in June, the U.S. Fish and Wildlife Service classified captive chimps in the U.S. as an endangered species, so any experiments on the remaining 50 chimps would have had to been OK’d by that agency.

Now, the NIH will spend the next couple of years relocating the chimps from facilities in Texas. Most, if not all of them, will end up in a 200-acre federal chimpanzee sanctuary in Keithville, Louisiana, called Chimp Haven. (If you haven't watched the video below of chimps exploring their new environment at Chimp Haven — literally stepping on grass and seeing the sky for the first time in their lives — it's worth a watch.)

The 50 chimps, now housed in facilities throughout Texas, are not the only ones that will eventually need homes. More than 150 other chimps, supported by the NIH but not owned by the government, will need to be relocated, according to Nature. And there are more chimps out there that need a home, the Humane Society’s Pacelle said in his blog post.

“Approximately 700 chimpanzees remain in laboratories with around 300 owned by the federal government.” he wrote. “But we are working on travel plans for every one of them … The HSUS stands ready to work with stakeholders, including the government, Chimp Haven and other sanctuaries, laboratories, the public, and other animal protection groups, to ensure all chimpanzees are retired to high-quality sanctuaries.”