becoming widespread in the 1920s. Such covenants were employed by many real estate developers to "protect" entire subdivisions, with the primary intent to keep "white" neighborhoods "white". Ninety percent of the housing projects built in the years following World War II were racially restricted by such covenants. Cities known for their widespread use of racial covenants include Chicago, Baltimore, Detroit, Milwaukee, Los Angeles, Seattle, and St. Louis. The Chicago suburb of Cicero, for example, was made famous when Civil Rights advocate Rev. Martin Luther King Jr. led a march advocating open (race-unbiased) housing. Within employment, economic opportunities for blacks were routed to the lowest-status and restrictive in potential mobility. In 1900 Reverend Matthew Anderson, speaking at the annual Hampton Negro Conference in Virginia, said that "...the lines along most of the avenues of wage earning are more rigidly drawn in the North than in the South. There seems to be an apparent effort throughout the North, especially in the cities to debar the colored worker from all the avenues of higher remunerative labor, which makes it more difficult to improve his economic condition even than in the South." In the 1930s, job discrimination ended for many African Americans in the North, after the Congress of Industrial Organizations, one of America's lead labor unions at the time, agreed to integrate the union. School segregation in the North was also a major issue. In Illinois, Ohio, Pennsylvania, and New Jersey, towns in the south of those states enforced school segregation, despite the fact that it was prohibited by state laws. Indiana also required school segregation by state law. During the 1940s, NAACP lawsuits quickly depleted segregation from the Illinois, Ohio, Pennsylvania and New Jersey southern areas. In 1949, Indiana officially repealed its school segregation law as well. The most common form of segregation in the northern states came from anti-miscegenation laws. The state of Oregon went farther than even any of the Southern states, specifically excluding blacks from entering the state, or from owning property within it. School integration did not come about until the mid-1970s. As of 2017, the population of Oregon was about 2% black. In Alaska Racial segregation in Alaska was primarily targeted at Alaska Natives. In 1905, the Nelson Act specified an educational system for whites and one for indigenous Alaskans. Public areas such as playgrounds, swimming pools, and theaters were also segregated. Groups such as the Alaska