This D3.js v4 visualization displays the quarterly gross domestic product of the United States from 1947 to 2015 as a series of vertical bars. An interactive tooltip reveals the exact date and GDP value in billions of dollars for each quarter. The chart uses `d3.scaleTime` for the x-axis, `d3.scaleLinear` for the y-axis, and `d3.axisBottom` and `d3.axisLeft` to render the axes. Data is sourced from the FreeCodeCamp GDP-data JSON file hosted on GitHub. Animated transitions enhance the tooltip and overlay effects.