Carbon Brief has distributed a racing graph that shows the countries with the largest cumulative CO2 emissions since 1750. At the end are the rankings as of the end of 2018/start of 2019.
Data are in Mt, though by the end every country has produced many Gt.
UK led until just before World War One. USA then led. It finished 1st at 397 Gt.
UK dropped out of second and replaced by USSR around 1975.
Germany passed UK in 1982.
China passed UK in 1999, Germany in 2001, and USSR/Russia in 2014. It ended at 214 Gt.
Canada entered the race in 1908 and finished 9th (32 Gt) despite it relatively small population.