For decades, though, census officials denied that they had played any role in providing information.
According to Anderson and Seltzer, the Federal Bureau of Investigation and military intelligence agencies began pushing in late 1939 to relax census confidentiality rules in the hope of accessing data on individuals. But the effort was opposed by Census Bureau Director William Lane Austin.
After the 1940 presidential election, however, Austin was forced to retire. He was replaced by J.C. Capt, who backed efforts to remove confidentiality provisions. Capt’s efforts helped clear the way for other agencies to access the information on Japanese Americans.
In 2000, Anderson and Seltzer found documents that showed officials with the Census Bureau had provided block-level information of where those of Japanese ancestry were living in California, Arizona, Wyoming, Colorado, Utah, Idaho and Arkansas.
The revelations prompted Kenneth Prewitt, then director of the U.S. Census Bureau, to issue a public apology.
Anderson and Seltzer, however, weren’t finished. They suspected that despite the bureau’s denials, it had also released “microdata” — information about individuals, including names and addresses.
In 2007, they found proof, uncovering documents that showed Census Bureau officials provided names and addresses of individuals of Japanese ancestry
Monday, July 8, 2019
"Secret use of census info helped send Japanese Americans to internment camps in WWII"
WaPo from 2018: