Note that Johan Beckström's place of residence is already given as America when he departs via Trondheim in March (in contrast to his wife and son who were still residents of Sweden). I suppose this means Johan had already travelled to America before 1902 and found a house for himself and his family?
Also, while Minneapolis is obviously Johan's ultimate destination, Boston may merely be the port of entry of his wife and son, since I suppose they were going to the same destination anyway. Thus perhaps Johan's 1902 journey went via Boston as well, if he can't be found in Ellis Island records? Are there similar ship manifests archived in Boston, waiting to be scanned and placed online?