US Population Density Growth Over Time

This application demonstrates how the population density of US counties evolved from 1790 to 2020, using the US Census Bureau's 2019 ACS data as a baseline, and applying exponential decay for earlier decades. The interactive map allows you to explore density changes nationwide over time.

Population Density Preview

Features

  • Interactive timeline slider to select any decade between 1790 and 2020
  • County-level choropleth showing density categories from rural to highly urbanized
  • Tooltips on hover displaying county name, state, and density metrics
  • Local caching of geometry and population data to improve load performance
  • Ability to download static PNG images of the current map

Technical Stack

  • Python (Streamlit) for rapid web-based data apps
  • Pandas and NumPy for data manipulation and exponential decay modeling
  • GeoPandas for shapefile processing in Albers Equal Area projection
  • Plotly for interactive choropleth maps and integrated exporting
  • Census Bureau ACS API for baseline population data
  • Requests for fetching geometry and shapefile zip data