Hedmark was a county in Norway before 1 January 2020, bordering Trøndelag to the north, Oppland to the west, Akershus to the south, and Sweden to the east. The county administration is in Hamar. Hedmark made up the northeastern part of Østlandet, the southeastern part of the country. It had a long border with Sweden to the east. The largest lakā¦Hedmark was a county in Norway before 1 January 2020, bordering Trøndelag to the north, Oppland to the west, Akershus to the south, and Sweden to the east. The county administration is in Hamar. Hedmark made up the northeastern part of Østlandet, the southeastern part of the country. It had a long border with Sweden to the east. The largest lakes were Femunden and Mjøsa, the largest lake in Norway. Parts of Glomma, Norway's longest river, flowed through Hedmark.