important for the emerging industrial centers, most of which were located in the Prussian regions of the Rhineland, the Saar, and the Ruhr valleys. States more distant from the coast joined the Customs Union earlier. Not being a member mattered more for the states of south Germany, since the external tariff of the Customs Union prevented customs-free access to the coast (which gave access to international markets). Thus, by 1836, all states to the south of Prussia had joined the Customs Union, except Austria. In contrast, the coastal states already had barrier free access to international trade and did not want consumers and producers burdened with the import duties they would pay if they were within the Zollverein customs border. Hanover on the north coast formed its own customs union – the “Tax Union” or Steuerverein – in 1834 with Brunswick and with Oldenburg in 1836. The external tariffs on finished goods and overseas raw materials were below the rates of the Zollverein. Brunswick joined the Zollverein Customs Union in 1842, while Hanover and Oldenburg finally joined in 1854 After the Austro-Prussian war of 1866, Schleswig, Holstein and Lauenburg were annexed by Prussia and thus annexed also to the Customs Union, while the two Mecklenburg states and the city states of Hamburg and Bremen joined late because they were reliant on international trade. The Mecklenburgs joined in 1867, while Bremen and Hamburg joined in 1888. Roads and railways By the early 19th century, German roads had deteriorated to an appalling extent. Travelers, both foreign and local, complained bitterly about the state of the Heerstraßen, the military roads previously maintained for the ease of moving troops. As German states ceased to be a military crossroads, however, the roads improved; the length of hard–surfaced roads in Prussia increased from in 1816 to in 1852, helped in part by the invention of macadam. By 1835, Heinrich von Gagern wrote that roads were the "veins and arteries of the body politic..." and predicted that they would promote freedom, independence and prosperity. As people moved around, they came into contact with others, on trains, at hotels, in restaurants, and for some, at fashionable resorts such as the spa in Baden-Baden. Water transportation also improved. The blockades on the Rhine had been removed by Napoleon's orders, but by the 1820s, steam engines freed riverboats from the cumbersome system of men and animals that towed them upstream.