Shows with the longest “gestation” period before setting foot on a stage

What are some of the longest development periods for a Broadway show? Whether that means from first reading to first performance in front of a live audience or getting on Broadway. I know The Visit had a long period of time between its first tryout and the eventual Broadway run.

A Tale of Two Cities

Jill Santoriello began working on that show in the late 80s. There was a concert style production done by invitation only in the mid-90s. It was first optioned by producers for a Broadway production in the late 90s. There was an out of town tryout in Chicago scheduled for sometime in 2005/2006 that was scuttled due to a lack of funding. It then received an out of town tryout in late 2007 at the Asolo Rep in Sarasota. It finally opened on Broadway at the Hirschfeld about a year later in the fall of 2008.

SATURDAY NIGHT feels like the obvious answer. That was never produced prior to 2nd Stage right? And even then, it’s more of an interesting artifact than a great work of art.

I believe the musical which would ultimately become GRAND HOTEL got as far as an out-of-town tryout in the 50’s but ultimately didn’t make it to Broadway until the late 80’s.