More detailed interactive version

I saw this post from months ago about acid rain. Everyone who answered in the comments pretty much told the same story and the data seems to back them up.

Sulfur dioxide helps cause acid rain. When sulfur dioxide (SO₂) and sulfate aerosols in the air dissolve into cloud droplets and precipitates onto the soil, you get what's called wet sulfate deposition. Wet sulfate deposition (a primary indicator of acid rain) is the transfer of sulfate from the atmosphere to Earth's surface through rain, snow, or fog.

Power plants covered by EPA’s programs dramatically reduced their emissions while maintaining nearly the same electricity output. Pollution controls and a shift toward lower-emitting fuels helped drive the change.

In the last ~20 years, wet sulfur deposition decreased by 73%. While the acid rain issue is seeing progress, ecosystems are still recovering.

EPA’s explanation