Looking for Anne and Marit Olsdatter

My greatgrandfather had two sisters who left for America, but we do not know where or when. Their names were Anne Olsdatter, born 1862 in Heidal, Vågå, and Marit Olsdatter, born 1868, same place. My greatgrandfather (born 1865/66) also left for America, in 1892, but he came back to Norway in 1899. He did not speak much about his time in America. We think he was at the same place in USA as his sisters, one of the women died before he came, the other one took over his farm when he left for Norway. But this is something my father THINKS he has heard when he was young, can not say if it is correct or not. All the three names are very common, this is a problem when looking for them... They might have used Sagstuen as lastname, since the farm in Norway had that name. Can anyone help?