Emigration from north German ports developed slowly with sources of migrants began to shift to north and east in the 1830s in the ports of Hamburg and Bremen. The river system of Weser offered transportation for emigrants to Bremen. The building of railroads in the late 1830s offered alternative routes for migrants from the interior German states and thus competition for these northern German ports. The result was to provide cargoes of emigrants for ships arriving in the ports with American commodities, so they would not have to return empty or seek cargo in other ports.
Bremen had already in the 1820s established itself as the center of tobacco trade between America – especially Baltimore- and Germany, replacing Dutch ports as the principal entry point for tobacco in all northern Europe. However at about the same time the accumulation of silt in the Weser River began to impend the movement of oceangoing vessels. To avoid this growing problem the city in 1827 built a new town called Bremerhaven (near mouth of Weser river and opened this port in 1830. Gradually New York city in 1840s replaced Baltimore as the chief American port connecting to Bremen.