Which C.S. Lewis book opened The Chronicles of Narnia in its original publication order?

The Lion, the Witch and the Wardrobe opened The Chronicles of Narnia in its original publication order.

Macmillan published the book in 1950, making it the first Narnia novel released to readers. It introduces the Pevensie children, the land of Narnia, the White Witch, and Aslan. The story begins when Lucy Pevensie discovers a passage into Narnia through a wardrobe.

Lewis later wrote The Magician’s Nephew as a prequel explaining Narnia’s creation, and modern editions have sometimes numbered it first according to the fictional chronology. That creates a frequent ordering confusion. The Magician’s Nephew is chronologically earliest in the story world, but The Lion, the Witch and the Wardrobe was the first published Narnia book.

The novel’s title refers to Aslan, the White Witch, and the wardrobe that connects the children’s world with Narnia. Its success led to six further books in the series.