At that time, developers made southern Oakland County a suburb of Detroit; a Cincinnati firm platted a section of Royal Oak called "Urbanrest." Migration worked both ways. Several thousand people moved from Oakland County farms to Detroit as the city attracted factories. By 1910, a number of rich Detroiters had summer homes and some year-round residences in what became Bloomfield Hills. The auto age enveloped Pontiac in the early 1900s. The Oakland Motor Car Company was founded in 1907 and became a part of General Motors Corp., which was soon Pontiac's dominant firm.