"In the Year 2525" hit number one on the pop charts in 1969. It claimed the #1 spot for six weeks, a remarkable achievement. It also topped the charts in the UK. Coincidentally, it was number one on July 20, 1969 in the USA, the date of the first manned moon landing by astronauts Neil Armstrong and Buzz Aldrin. It was nominated for a special Hugo Award that same year.
It is not typical for a recording artist to have a number one hit single and then never have another chart single for the rest of their career.
Wikipedia has the story.