Norwegian Roots

The problem with taking the train from Oslo to some place closer to Hedalen is that you're unlikely to find a car rental agency in any location that would make this plan significantly more convenient than driving straight from Oslo. You didn't mention if you've ever visited Norway before, but if not... the interior of the country is VERY sparsely populated. Even more so than Sweden, and that's saying something. Viamichelin shows a driving time of about 2.5 hours from either downtown Oslo or the airport. I tried putting in some other towns in the general region that might be large enough to have at least one rental car agency (Hamar, Gjøvik, Hønefoss), and none of them are much more convenient than Oslo. If you're traveling in the winter, there's a regular bus between Oslo and the ski resort of Hemsedal, but once again, the drive from there to Hedalen isn't much more convenient than from Oslo.

Thank you for your help! It looks like I will need to be brave and drive from Oslo. I've done more research and my ancestors owned farmland in Hedalen and Bagn. We'd like to stay somewhere that would be convenient so we can explore the area, but as you mention, it looks like the area is very rural. If anyone has any suggestions about lodging I would appreciate it! We are traveling in early July. Thank you!

I do not have any suggestions for lodging there, but I will assure you that driving in Norway is very easy.

Speaking of driving... ask the rental agency how the toll roads work. Norway gets my vote for having the least intuitive toll collection system in the world.