What year did the Arrow of Light become the highest rank in Cub Scouting?

When the Cub Scouts was first established in 1930 the three ranks were Wolf, Bear and Lion. In 1941 the WEBELOS badge was added for 10 year old boys who had finished the Lion badge (it went by age then - not school year as we do it today). Its symbol was what we now use for the Arrow of Light.

In 1967 the Lion Rank was dropped and the 10 year old Cubs were known as WEBELOS. The badge still looked like our Arrow of Light. Around 1972 they changed the name of the WEBELOS rank badge to the Arrow of Light.

The five ranks as we know them today, Bobcat, Wolf, Bear , WEBELOS, and Arrow of Light were established in in 1978.