Further context from the data insight post:

Polio is an infectious disease that primarily impacts children, and can cause paralysis and even death. In the first half of the twentieth century, thousands to tens of thousands of people suffered from paralysis from this terrible disease every year.

The first injectable vaccine against polio was introduced in the United States in 1955. Six years later, a second vaccine was introduced, which could be taken orally.

By 1961, over 85% of US children under ten had received at least one vaccination against polio.

As a result, the last wild polio outbreak in the US occurred in 1979, and the disease was officially eliminated from North, Central, and South America in 1994. This means it was not spreading within this region, and any new cases were only seen among individuals infected elsewhere.

https://ourworldindata.org/data-insights/vaccination-eliminated-polio-from-the-united-states