A person from Trøndelag is called a Trønder. The largest city in Trøndelag is the city of Trondheim. The administrative centre of the county is Steinkjer, although Trondheim is the seat of the county mayor. This is to make the county more efficient and not too centralized, as Trøndelag is the second largest county in Norway.
The old Trondhjems amt county was divided into two administrative counties in 1804 by the King of Denmark-Norway. In 2016, the two county councils voted to merge into a single county in 2018.
Trøndelag is one of the most fertile regions of Norway, with large agricultural output. The majority of the production ends up in the Norwegian cooperative system for meat and milk, but farm produce is a steadily growing business.
The Old Norse form of the name was Þrœndalǫg. The first element is the genitive plural of þrœndr which means "person from Trøndelag", while the second is lǫg (plural of lag which means "law; district/people with a common law" (compare Danelaw, Gulaþingslǫg and Njarðarlǫg). A parallel name for the same district was Þróndheimr which means "the homeland (heim) of the þrœndr". Þróndheimr may be older since the first element has a stem form without umlaut.