Settlers established commercial fisheries on the north coast of the lake around the 1850s. An important business was fishing. In the pre-Civil War years, railways sprouted everywhere, and around 1852 there were railways circling the lake. Maritime traffic picked up, although the lake was usually closed because of ice from December to early April, and ships had to wait for the ice to clear before proceeding. Since slavery had been abolished in Canada in 1833 but was still legal in southern U.S., a Lake Erie crossing was sometimes required for fugitive slaves seeking freedom: