I noticed that Tom Petty & the Heartbreakers finally hit number one last year in the US with Hypnotic Eye, their 13th studio album. Is this a record? If not, which artist has released the most original studio albums (i.e. not live albums, compilations or reissues), in any given country, before finally getting their first number 1 album (in that same country)?
I believe I've found an answer to this that should be very hard to counter: David Bowie. The last release in his lifetime, Blackstar, was put out on January 8, 2016, two days before his death. It was his 25th studio album, and his first to hit #1 in the United States, bringing the number to beat up to 25.