Julian Fellowes’ “The Gilded Age” is improving in the ratings and in its production. Originally planned for NBC, the period drama soap opera had a clunky start but it’s picked up in its five episodes.

However, last night’s episode offered a glaring historical error.

You see, Ellis Island didn’t open until 1892. “The Gilded Age” takes place in 1882.

In an early scene in episode 5, Christine Baranski, Cynthia Nixon, and Louisa Jacobson are riding to some event, and Louisa’s character is explaining to Baranski’s all the new people who will be some event.

Baranski’s wonderfully haughty Agnes van Rhijn replies, “Who’ll be going The latest arrivals from Ellis Island?”

Only seagulls and pigeons were living on Ellis Island in 1882, Agnes. Ouch! This is a common mistake in our times to think that every immigrant who came to America arrived via Ellis Island, which is now a historical museum. But for example, my ancestors came from Eastern Europe and London prior to 1892 and through different ports. Only one of my grandparents’ families landed there, in 1913.

Julian Fellowes and his team always did a wonderful job with historical facts on “Downton Abbey.” But when there was a mistake like this one, they took umbrage. He once said of the errors,“The real problem is with people who are insecure socially, and they think to show how smart they are by picking holes in the program to promote their own poshness and to show that their knowledge is greater than your knowledge.”

“Mad Men,” which was set in the 1950s, sometimes goofed as well. And I’m sure “Mrs Maisel” has, too. But Aunt Agnes will have to wait another decade before she can make such an elitist statement.

PS It hasn’t been said yet, but I do think when Agnes refers to “new” people, she’s referring to Jews. It hasn’t been explicit yet, but the Russells — or at least Mr. Russell — is Jewish. And in last night’s episode he asked his daughter’s suitor if he would mind working for a Jewish financial firm.

Everyone must have been watching “Euphoria” and “Billions” last night. Because they weren’t watching broadcast TV, that’s for sure.

The Winter Olympics on NBC ended with a whimper, just 5.04 million viewers.

It was worse on ABC where Questlove’s “Summer of Love” had a meager 1.5 million. This was Disney using ABC to promote a Searchlight movie for Hulu and maybe find some Oscar votes in the process. But it didn’t work out. I may have been the only person who watched it. “Summer of Soul” deserves an Emmy award after last night’s showing. It’s a great archival doc that continues to insist its material was “lost” and “found.” This is not true.

We don’t have the numbers for “Euphoria” yet, but the episode was all about Lexi’s school play. These “kids” (they’re in their 20s) go to a high school that looks like it spent $50,000 or more on the class musical.

Meanwhile, the internet theory is that Zendaya’s Rue is already dead from a drug overdose and is watching all this from the great beyond. Certainly last night there were what I would call “Paul is dead” clues: a funeral in Lexi’s play (it was for Rue’s dad) and the way Rue sat alone at the show and just made faces. Who knows? Maybe they’re all dead. If any of us had gone through high school this way, no one would made it to graduation.

Tomorrow, cable ratings.