Ansel Adams and Dorothea Lange's photos of camps where Japanese-Americans were incarcerated in WW2

Seventy-five years ago, US President Franklin D Roosevelt signed Executive Order 9066 which authorised the imprisonment of Japanese Americans. Roughly 120,000 Japanese immigrants and Japanese-Americans were sent to desolate camps that dotted the West because the government claimed they might plot against the US. Thousands were elderly, disabled, children or infants too young to know the meaning of treason. Two-thirds were citizens. The United States had entered World War Two after Japan's surprise attack on Pearl Harbor about three months earlier.

A year-long exhibition of photos – many by famed photographers Ansel Adams and Dorothea Lange – has opened at the Smithsonian's National Museum of American History in Washington, DC. They show the dislocation and loss of freedom of these American citizens who had been uprooted from their homes.

Neatly dressed men in jackets and ties queuing on city streets next to luggage and sacks on their way to camps. Children sitting on bundles of their families' belongings. Dusty and desolate barracks. A detainee driving a tractor in a prison camp field. Neatly dressed men lining up for lunch at Manzanar War Relocation Centre, now a national historical site.

The story of the camps and the people confined in them, the result of wartime racial profiling, is an underreported chapter in US history.

President Franklin D Roosevelt signed Executive Order 9066 on 19 February 1942, to protect against espionage and sabotage. Notices appeared ordering people of Japanese descent to report to civil stations for transport. Desperate families sold off belongings for cheap and packed what they could. The luckier ones had white friends who agreed to care for houses, farms and businesses in their absence.

Joyce Okazaki (née Nakamura) was seven years old in 1942 when her family left their Los Angeles home and reported to a World War Two internment camp for Japanese Americans in California's remote desert. She recalls crowded rooms filled with cots and embarrassment that the toilets at Manzanar War Relocation Centre had no privacy. "Like Nazi Germany, we Japanese Americans were put into concentration camps," said Okazaki, now 82, while recognising that detainees were not killed or tortured. "We were constantly under threat if we went near the barbed wire fences."

Okazaki's experience is captured in a photograph of her and her sister and their mother at Manzanar, an image preserved in a Library of Congress archive. Okazaki recalls a life of fear in the camp. "With barbed-wire fences and guard towers and sentries with rifles manning them, you become scared," she said.

Okazaki and her family left in July 1944. Their families were required to swear a loyalty oath to the United States to regain their freedom. Okazaki objects to the term internment and prefers incarceration or imprisonment. "I was not an internee because I am a citizen. The definition of internment refers to enemy aliens in time of war," she said.

Actor George Takei, who played Sulu in the 1960s television show Star Trek, recalls arriving at a camp at Santa Anita Park horse racetrack, just a short trip from his Los Angeles home. "When we were first ordered out of our homes by the soldiers, we were taken to Santa Anita racetrack and herded over with other Japanese American families to the stable area and assigned a horse stall for us to sleep in. From a two-bedroom home on Garnet Street in Los Angeles to a smelly – I mean, it was pungent with horse manure."

As survivors commemorate the 75th anniversary of the executive order that authorised their incarceration, they're speaking out to make sure that what happened to them doesn't happen to Muslims, Latinos or other groups. They're alarmed by recent executive orders from President Donald Trump that limit travel and single out immigrants. In January, Trump banned travellers from seven majority Muslim nations from entering the US, saying he wanted to thwart potential attackers from slipping into the country. Although a federal court halted the ban. Trump has said a he would issue a replacement order.

"On January 27, another president of the United States Donald Trump signed another executive order. That executive order had behind it the same animus and prejudice and ignorance that was in the first 9066 executive order. But it is a different America today. Immediately, massive crowds of Americans rushed to their airports, crammed into the airports, and resisted, opposed that executive order," said Takei.

The Japanese American Citizens League and other groups say the government used euphemisms such as "internment", "evacuation" and "non-alien" to hide the fact that US citizens were incarcerated and the Constitution violated. These groups say this White House has what they see as the same dangerous and flippant attitude toward the Constitution. Japanese-American politicians expressed horror when a Donald Trump supporter cited the camps as precedent for a Muslim registry.

The Japanese American Citizens League "vehemently" objected to executive orders signed by Trump last month, to build a wall along the Mexican border, punish "sanctuary" cities that protect people living in the country illegally, and limit refugees and immigrants from entering the country. "Although the threat of terrorism is real, we must learn from our history and not allow our fears to overwhelm our values," the statement read in part.

Orders against Japanese-Americans were revoked after the war ended in 1945. They returned to hostility and discrimination in finding work or places to live. A congressional commission formed in 1980 blamed the incarceration on "race prejudice, war hysteria and a failure of political leadership." In 1988, President Ronald Reagan signed a bill to compensate every survivor with a cheque for $20,000 (£16,114) and a formal apology from the US government.