Over the past century, millions of Americans have taken to the streets to demand change — for the right to vote, for civil rights, for fair wages, for disability access, for gay liberation, and for a long list of causes that shaped the country we live in now. Some of those movements are instantly recognizable. Others have been largely forgotten. But looking at the photos of these protests, something else stands out. A march from 1970 for abortion rights could almost pass for a rally last year. A 1977 sit-in by disability activists uses the same tactics and language advocates rely on today. A 1968 image of Black sanitation workers holding signs that read "I AM A MAN" captures a demand that still hasn't fully been met. What makes these images so striking isn't just their historical significance. It's how familiar they feel, and how consistently people have shown up, again and again, to push for something better. Some of what these people were fighting for has been won. Some of it hasn't.…