In 1860, the Philological Society launched its effort to create a dict

Yes, but note that we are shifting our frame of reference to today when we use these tenses.

In 1860, PS launched its effort to create a dictionary more comprehensive than the world had ever seen;
although the project would take more than 60 years to complete, the Oxford English Dictionary was born. (Our perspective is 1860. Looking from there, the project would take more than 60 yrs to complete but the OED was born)

In 1860, PS launched its effort to create a dictionary more comprehensive than the world had ever seen.

Although the project took more than 60 years to complete, the Oxford English Dictionary had been born. (We are looking at it today. The OED project took 60 yrs to complete (from 1860 to 1920) but the OED had been born in 1860.)