The bigotry official America so often shows toward so many hard-working immigrants never really goes away. The specific ethnic groups who suffer the most just change from time to time.

Just the other day, and about 149 years too late, the descendants of some of the thousands of Chinese immigrants who did so much to build the first Transcontinental Railroad were included in the celebration of that nation-building milestone.

Our nation was happy to use the hard manual labor of those immigrants to carry out the shorter, but much more difficult and dangerous, segment of the railroad. That was the part that involved drilling and blasting and tunneling through the Sierra Nevada mountains in building the line from Sacramento to the join-up point in Promontory Summit in northern Utah.

There — on May 10, 1869 — the eastbound Central Pacific line met the westbound Union Pacific track, laid all the way across the plains from Omaha, Neb., by thousands of mostly Irish workers. The Golden Spike was driven. There was champagne. There were commemorative photographs taken. There was much rejoicing.

Though not for the Chinese workforce. They were excluded from the party, and from the familiar photographs. And a great many of them were later ejected from the nation, as racism and a fear of surplus labor built a trend toward the passage of the Chinese Exclusion Act of 1882.

Only this year, after several tries, were the descendants of those workers invited to participate in the celebration and picture-taking. And they are to be included in next year’s 150th anniversary party as well.

So, how many years will it take for the United States to live down the horrid treatment being visited upon migrants from Central America?

The newest way to discourage undocumented immigration is the official policy, outlined by no less a personage than Attorney General Jeff Sessions, to hold adults caught crossing the border in facilities separate, perhaps many miles apart, from their accompanying children. That’s not border security. That’s child abuse.

Meanwhile, John Kelly, the White House chief of staff, mused aloud about why we need to step up enforcement of immigration laws. Because, basically, those kind of people aren’t our kind of people.

They don’t speak English, Kelly said. They don’t assimilate. They don’t have valuable skills. We ought to keep them out.

Well, it is true that many of them don’t speak English. Yet. But neither did the ancestors of a great many Americans. There is no reason to accept the slander that today’s migrants are any less hardworking, any less devoted to making a better life for themselves and their children and, in the process, the whole nation, than were those previous waves of immigration that included Kelly’s ancestors and, quite likely, yours.

Like all those people who built that railroad, today’s immigrants are going to build the intellectual, physical and cultural infrastructure for the next generation of Americans.

It is just a question of whether we will be, 149 years hence, ashamed of the way we treated them. Or proud.