The source of the original data is Bureau of Economic Analysis, an agency of the United States Department of Commerce.
BEA defines disposable personal income as: “After-tax income. The amount that U.S. residents have left to spend or save after paying taxes is important not just to individuals but to the whole economy. The formula is simple: personal income minus personal current taxes.” This chart shows disposable personal income on a per-person basis, and also adjusted for the effects of inflation.
Of note are the significant blips in the Trump and Biden administrations, reflecting the stimulus payments each enacted.
Click chart for a larger version.