Anne of Green Gables, on CBC (Canada) / PBS (USA)
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Based on the books by Lucy Maud Montgomery. I guess this aired on the anthology series WonderWorks in the U.S., but I'm not sure if I saw it there or just on CBC. I know I read the original book in... fourth grade, I think, but I can't quite remember if that was before or after I saw the miniseries. Anyway, it's about an orphan named Anne Shirley, who wound up, sort of by mistake, living with Matthew Cuthbert and his sister Marilla. They wanted to adopt a boy to help on the farm. Oh well, they ended up loving her, anyway. She was quite an interesting individual. Very smart, an independent thinker, very romantic in a way, but also kind of afraid of romance. Her best friend was Diana Barry. And there was a boy named Gilbert Blythe, with whom Anne had a... complicated relationship. Anyway, I loved the miniseries. And Anne was played by Megan Follows, who ended up becoming one of my favorite actors ever.
Sequels include Anne of Avonlea (IMDb; Wikia; Wikipedia), which I must have watched on CBC, and Anne of Green Gables: The Continuing Story (IMDb; Wikia; Wikipedia), which I think I saw on PBS. Someday I should rewatch the various miniseries, so I can write proper reviews of each. And there was a TV movie in 2008, Anne of Green Gables: A New Beginning, which I've never seen, but would like to.
There's also a related TV series called Road to Avonlea, based on Montgomery's books, set in the town of Avonlea, some while after Anne and grown up and moved away. And in 2016, there was a remake of the original story, L.M. Montgomery's Anne of Green Gables.