The Swedish-Norwegian border has fluctuated considerably through the history of the two nations, both because of poor delineation, weak state power and landscapes changing hands. If you go all the way back to the medieval era and before things tend to get more difficult to define still. Was there any particular time period you were interested in?

Sovreignty over Jemtland/Jamtland/Jämtland was transferred to Sweden from Denmark-Norway as part of the 1658 Treaty of Roskilde, which brought the first phase of the Little Nordic War to an end. The same treaty also ceded the Norwegian landscapes of Bohus, Herjedalen/Härjedalen and Trøndelag/Tröndelag (the last of which at the time corresponds fairly accurately to the modern day area of South and North Trøndelag and Nordmøre).

Trøndelag would be ceded back to Denmark-Norway by the Treaty of Copenhagen only two years later, but Bohus, Härjedalen and Jämtland have remained Swedish landscapes since 1658.