America in the Gilded Age was a starkly unequal place, not just in terms of inequality between people but inequality between regions. Long-settled, fast-industrializing states in the Northeast were far richer than those of the West or the South, which had many fewer factories, railroads, and other kinds of capital goods that allowed for productive work and high wages. But around 1880 that began to change, and for 100 years, income gaps between states slowly converged at a rate of about 1.8 percent per year.
But since 1980, that process has began to slow, and over the past decade it’s essentially stopped entirely. Today, Massachusetts’s GDP per capita is about double what you find in Mississippi — roughly equivalent to the gap between Switzerland and Slovakia — and it’s not getting any narrower.