The novel took him over 14 years to write. After he wrote the Hobbit in 1937, it wasn't until the mid 1950s when the first volume "The Fellowship of the Ring" was actually published.
When all was said and done, the book was over 1200 pages that he typed himself! It is said that when he needed a copy of the manuscript, he didn't have the resources to make one, so he retyped the whole thing himself.
The craziest thing is that he wasn't a particularly adept typer, so he pecked his way through the 1200 using only two fingers!