Around 1838, the state of Michigan started to build the Southern Railroad, running from Monroe on Lake Erie west to New Buffalo on Lake Michigan. The first section, from Monroe west to Petersburg, opened in 1839. Extensions opened in 1840 to Adrian and 1843 to Hillsdale. On May 9, 1846, the partially completed line was sold to the Michigan Southern Rail Road, which changed the planned western terminal to Chicago using the charter of the Northern Indiana Railroad. The grading that had been done was not used, as the grade was too steep, and instead the original Buffalo and Mississippi Railroad charter was used west of La Porte, IN. The Michigan Southern leased the Erie and Kalamazoo on August 1, 1849, giving it a branch to Toledo, OH and a connection to planned railroads east from Toledo.