Which preposition to use with secularised

at Occurrences 1%

The Bishopric of Fulda was formerly an independent ecclesiastical state, but was secularised at the treaty of Lunéville and now forms part of the territory of Hesse-Cassel.

in Occurrences 1%

OSNABRÜCK (35), a town in Hanover, 70 m. W. of Hanover, with a bishopric founded by Charlemagne, which was held by a brother of George I., and was secularised in 1803.

Which preposition to use with  secularised