The Nascar Monstr Energy Nascar Cup Series is the most popular and the most profitable series. It started off as the Strictly Stock Series. In 1971, it became the Winston Cup Series. In 2004, it changed to the Nextel Cup Series. It was renamed as the Sprint Cup Series in 2006. In 2017, it was changed to what it's now known as the Nascar Monster energy Nascar Cup Series.