More than any other factor, it was the war against the Confederacy and the triumph of the Radical Republicans in the Union that set the North down the long road to becoming the integrated multiracial society that is so resented by White Nationalists.
Here’s an excerpt from Eric Foner’s Reconstruction (review coming in December or January) about how White racial attitudes were changed in the North during the postwar years:
“Partly because of Congressional measures that applied throughout the country, and partly due to actions at the state and local level, the decade following the Civil War witnessed astonishing advances in the political, civil, and social rights of Northern blacks. The Civil Rights Act of 1866 and postwar amendments voided laws barring blacks from entering Northern states, testifying in court, and voting, and were successfully employed by individuals pressing damaging claims against railroads and streetcars that excluded them altogether or barred them from first-class compartments. Although state courts generally held that segregated facilities, if truly equal, did not violate the Fourteenth Amendment, discrimination in transportation faded in many parts of the North. Pennsylvania’s legislature prohibited streetcar segregation in 1867 and New York Republicans six years later enacted a pioneering civil rights law that outlawed discrimination in public accommodations. Blacks also gained access to public schools in state that had previously made no provision for their education. Some cities with sizable black populations, like New York and Cincinnati, maintained separate schools, but others, like Chicago, Cleveland, and Milwaukee, not only operated integrated systems but occasionally employed a black teacher. In a few states, integrated education now became the norm. Michigan’s legislature outlawed school segregation in 1867 (although Detroit’s school board refused to comply for four years), and the state university admitted its first black students in 1868. And Iowa’s Supreme Court ruled separate schooling a violation of the Fourteenth Amendment.” …
Perhaps this was inevitable for a group mostly derived from the tiny black business class and representing a politically marginal constituency (blacks still comprised less than 2 percent of the North’s population). Although black politicos won seats in the Massachusetts and Illinois legislatures, most, with no realistic prospect of elective office, found themselves beholden for position to patronage from white Republicans.
Nonetheless, blacks now found the North’s public life open to them in ways inconceivable before the war. A recognition for their claim to equal civil and political rights had become so much a part of what it meant to be a Republican that no fewer than 90 percent of the party’s voters in New York State supported equal suffrage in an unsuccessful 1869 referendum.”
The North was only 2 percent black when the Radical Republicans passed the Civil Rights Act of 1866 (the first federal civil rights law in American history) which repealed the state laws in Indiana, Illinois, and Oregon which excluded or heavily fined the settlement of free blacks.
Before the War Between the States, Southern planters often came to the North to capture fugitive slaves and bring them back to the South. In response, Northern states like Massachusetts (the citadel of abolitionism) passed “personal liberty laws” to nullify the Fugitive Slave Act and keep a small and growing black population in the North.
In the space of twenty years (1860 to 1880), everything from black citizenship to black voting rights to black state legislators to repeal of the anti-miscegenation laws to repeal of the laws that banned free black settlement to integrated public education became the norm in the Northeast and Midwest.
Yankees had won the war. In every conceivable way, they proceeded to reconstruct the Union in their own image. What had previously been a New England regional peculiarity (i.e., black citizenship) was now enshrined in the Constitution in the form of the 14th Amendment.
The constitutional foundation had been laid for the mass migration of African-Americans to the Northern states. For several decades, it seemed as though Reconstruction would survive in the South, but after the Jim Crow system was created in the 1890s and 1900s, millions of blacks would start moving to Northern states like Michigan and Illinois.