What forest? Either it was owned by a noble with enough of an army to stop you, your great...grandparents already cut it, or the land wouldn't be useful for farming for some other reason.

North America had vast empty forests - but remember just before Europeans arrived disease (small pox) killed large portions of the population. We have very little recorded about what life was like before Columbus, but archeological evidence suggests that the land was already used to the max capacity of their technology. (Europe did bring technology to better use the land - for some definition of better. I'm not qualified to comment on why they didn't develop the technology, but there seems to be some interesting culture factors - perhaps you can find an expert)