The US military believes the bones are those of American servicemen and potentially servicemen from other United Nations member countries who fought alongside the US on behalf of South Korea during the Korean war.
Resting inside coffins wrapped in US flags, the remains arrived from South korea at the US Naval Base Pearl Harbor in Hawaii, where a ceremony presided over by the country's Vice President, Mike Pence, was held.
There was some initial uncertainty over the fate of the remains, as North Korean officials canceled a meeting last month to discuss how to go about returning them.
According to officials, North Korea returned the 55 boxes of remains with only a single military dog tag and no other information that could help forensics specialists to identify the remains, the Associated Press reports. They set the caskets gently on risers lined up inside the hangar as Mr Pence stood watching with his hand over his heart.
After 65 years of conflict, North Korean leader Kim Jong-un made a commitment to US President Donald Trump and returned the remains of the fallen.
"And although today we are especially grateful to know the remains of these Americans killed in North Korea will finally be returning home, we are also very mindful of the approximately 5,300 still missing in Korea and the solemn debt our nation owes each and every one of them as well", Polk said.
It was the first repatriation of remains since 2005.
"The fact of the matter is that previous year, on President Trump's watch, North Korea made significant advances in its ballistic missile technology, achieving what many experts agree is a nuclear-capable operational ICBM", Menendez added.
"We see them going to work, just as before", one USA official told the Agency.
White House under fire for barring CNN reporter from event
He added that he would consider a visit to Washington but noted there must be "necessary conditions", without further explanation. The administration said "There was no plot to exclude Fox News , and they had the same interview that their competitors did".
The reports about new rocket development come after ongoing disclosures about a speculated uranium advancement office, called Kangson, that North Korea is working in mystery.
The North Koreans provided enough specifics about where each suspected body was found that USA officials have matched them to specific battles fought from 1950 to 1951, though not necessarily individuals, he said. Critics say the summit has so far failed to deliver on promised steps toward denuclearisation by Pyongyang.
Secretary of State Mike Pompeo also said Tuesday that reports of missile engine test facility dismantlement in North Korea are "entirely consistent" with the commitment Kim made to Trump in Singapore, and the USA has pushed for inspectors to be present.
United States defence secretary Jim Mattis said last week that the return of the 55 boxes was a positive step, but not a guarantee that the bones were American. In a joint statement during their summit, Kim and Trump pledged to "commit to recovering POW/MIA remains, including the immediate repatriation of those already identified".
The vice president spoke for a few minutes before the ceremony began, calling it "tangible progress in our efforts to achieve peace on the Korean Peninsula".
While the fighting in the Korean War lasted from 1950 until 1953, the war never formally ended because a treaty was never signed, though an armistice was struck dividing the peninsula in two.
On the issue of sanctions, however, Trump has been adamant, stressing on numerous occasions that North Korea should not expect an easing of restrictions any time soon.
The department left open the possibility that Secretary of State Mike Pompeo could meet North Korean officials during meetings of the Association of Southeast Asian Nations (ASEAN) bloc in Singapore this weekend.