Anniversary: Federal-Aid Highway Act of 1956 - why does this matter?

Summer travel is here and the Mass Pike or i90 is one of the major gateways. The interstate highway system grew over the years but was actually born on June 29. From the US Census:

"June 29 marks the anniversary of the Federal-Aid Highway Act of 1956. Observe this historic day with our activity “The Highway System” that uses an interactive data visualization to examine population density along Interstate 90."

Interactive data visualization
https://www.census.gov/dataviz/visualizations/031/

Anniversary: Federal-Aid Highway Act of 1956

More info on the Federal-Aid Highway Act of 1956
https://en.wikipedia.org/wiki/Federal_Aid_Highway_Act_of_1956