Froge
4 hours ago edited
"The Magicians Nephew" was written after the fact to tie everything together before the grand finally.
Order as written:
The Lion, the Witch and the Wardrobe (1950)
Prince Caspian: The Return to Narnia (1951)
The Voyage of the Dawn Treader (1952)
The Silver Chair (1953)
The Horse and His Boy (1954)
The Magician’s Nephew (1955)
The Last Battle (1956)

Order in the Narnia time sequence:
The Magician’s Nephew (1/1900)
The Lion, the Witch and the Wardrobe (1000-1015/1940)
The Horse and His Boy (1014/1940)
Prince Caspian (2290-2304/1941)
The Voyage of the Dawn Treader (2306-2310/1942)
The Silver Chair (2356/1942)
The Last Battle (2555/1949)

I also get the feeling the last three books written (Horse, Magician, Last) were written to cash in a bit more on the series popularity, though they are decent books they were out of place with the first four books. Personally I liked the "Voyage of the Dawn Treader", and "The Horse and his Boy."