What is pre-congregation canonization?

In the earlier times, saints were proclaimed to be saints by a local bishop, patriarch etc. and by popular devotion. Pre-congregation is when saints were canonized or declared to be saints, before the long and lengthy process that the Church has today to prove that they were saints, so the exact dates are not available.

They are called pre-congregational because they were declared saints before the Sacred Congregation for the Causes of Saints was instituted to investigate candidates for sainthood.