For more than a century, Pullman porters were a part of American train travel, until competition from planes and automobiles led to the decline of sleeper cars. Now the last generation of porters — who played a critical role in African-American history — is rapidly dying off. And Amtrak is attempting to locate the last few for National Train Day.

In 2001, the A. Philip Randolph Museum compiled a national registry of black railroad employees who worked from the late 1800s to 1969, a record that could be useful for historians and genealogists.

“There are a thousand people on this list — as we mark it up, it’s not looking like the same list anymore,” said Hank Ernest, who is coordinating the publicity for Amtrak. Asked how many they had found, he said, “Double digits.”

For his book “Rising From the Rails,” Larry Tye interviewed about two dozen former Pullman porters, so called because they worked for the Pullman Company, which made sleeper cars. “The youngest were in the 80s at that time, and the oldest were in their early 100s,” he recalled. In between the time he did the interviews and when his book came out in 2004, he estimated, a third of those men died. Another third have died since then, he estimates.

“The fact they are disappearing is taking with them a piece of American history,” Mr. Tye said.