This D3.js line chart visualizes customer counts per year from a CSV dataset, rendering an SVG line with steelblue strokes. The chart uses `d3.csv` to load data, `d3.scaleBand` for categorical years on the x-axis, and `d3.scaleLinear` for the y-axis. It applies `d3.axisBottom` and `d3.axisLeft` for labeled ticks, and draws the line via `d3.line` with custom positioning. Axes are labeled "Year" and "customers," and the code is structured as a reusable pattern inspired by Bostock’s chart conventions.