Agreed, Jackie Coogan is a contender.
There’s even a law named after him:
https://www.sagaftra.org/membership-benefits/young-performers/coogan-law
How about Robert Blake?
Definitely not. From roughly the same era (“ancient history”) as Shirley Temple, but I’d wager not a tenth as many people know who this is. And between having a law named after you, and having a freakin’ drink named after you, I know which one will earn your more fame.
I forgot about the drink.
kambuckta therefore wins the argument.
.
Now, I’m going to go make myself a double-strength Hayley Mills on the rocks…
I thought of Mara Wilson. She was in Mrs. Doubtfire, Miracle on 34th Street, and Matilda, which were all huge movies when I was growing up.
Between Shirley Temple and and Macaulay Culkin, I’d say Shirley Temple.
I would agree. To the extent that I remember Jackie Coogan today, it’s as Uncle Fester. That he started as a child actor is mostly a bit of trivia. I also tend to get him confused with Jackie Cooper, who also started as a child actor and continued to get work as an actor and director well into adulthood.
I would say that the answer is Shirley Temple, though I concede that a lot of younger folks today are probably unfamiliar with her.
I think Jerry Mathers as The Beaver should get at least an honorable mention.
That was Natalie Wood.
I was just about to post that. “Most-widely recognizable across generations” might be a better description for the Beav.
Charlie McCarthy was almost as famous as Shirley Temple. In terms of products, movies and radio programs, he is near the top.
But, was he made out of an adult tree, or a child tree?
Shirley Temple was the first person I thought of. Second was Elizabeth Taylor, who began her acting career when she was 9 years old.
Do you think 10% of Americans know who Mathers is? I suspect more know who Cotton Mathers is.
At one time, perhaps, but not now.
There are some other candidates; Miley Cyrus is a great one. But just listing a bunch of folks who were last famous when great-grandpa was a kid seems like a strange way to approach the question.
I think he was supposed to be a kid but he acted like an old man.
Who’s going to remember Miley Cyrus in 90 years? I couldn’t pick her out of a lineup even today.
Perhaps so, but “most famous” is an absolute.
Shirley Temple, and Shirley Temple Black, was a household name from the vaudeville era through movies, radio and TV. Miley Cyrus has some fame but she is not an icon.
Shirley Temple was one of the biggest stars in Hollywood, adult or child. Wikipedia says she was Hollywood’s number one box office draw. There’s just no comparison.
He was smart enough to stay wood! 
He was so long ago that I don’t remember a single political cartoon or wag using him to razz Kevin McCarthy.