“But I have promises to keep,

And miles to go before I sleep.” — Robert Frost

Sen. Richard Russell called it a work of “manifold evils.”

Sen. Barry Goldwater called it a “threat to the very essence” of America.

Rep. Howard Smith called it a “monstrous instrument of oppression.”

It was the Civil Rights Act of 1964, and its “oppression,” “threat” and “evil,” at least in the eyes of those conservative men, were that it outlawed racial discrimination in public places. The act was signed into law 50 years ago Wednesday by President Lyndon Johnson, and if it is not the single most consequential piece of legislation ever passed by Congress, it is certainly in the top tier.

Without the act, Barack Obama is no president, Neil deGrasse Tyson is no celebrity astrophysicist, Shonda Rhimes is no hit TV producer; somebody is legally required to enter McDonald’s through the back door, detour around a public park he is not allowed to walk through, or decide if seeing “22 Jump Street” is worth the indignity of watching it from the back row of the theater.

We have come a long way in the last half century. That is our triumph. And also our challenge.

Imagine you and a companion were driving from Miami to Seattle. That journey from diametrically opposed corners of the lower 48 is over a 3,300-mile drive. Now suppose you took a break roughly halfway through — Kansas City, let’s say — and your companion got out of the car, sat down with the air of somebody who doesn’t expect to move again and said with great satisfaction, “Boy, we sure have come a long way.”

It’s about 1,500 miles from Miami to Kansas City, so obviously she’d be right. But might you not be puzzled and perturbed by her sense of accomplishment? Might you not be inclined to point out that though you have, indeed, come a long way, you have a long way yet to go?

Perhaps, then, you can appreciate the frustration some of us feel when others of us proclaim with complacent satisfaction that “we have come a long way” in correcting America’s habit of racial bias — as if we did not have many miles yet to travel. Indeed, it has become an article of faith on the political right that racial bias has been well and truly vanquished. It’s a silly contention that does not survive the merest collision with statistical fact, but they make it anyway with the same sense of self-congratulation as that driver who is so pleased with herself at having reached Kansas City.

Each mistakes the way station for the destination.

If America is anything, it is an implicit promise of fairness, a promise that you will not be arrested, suspected, rejected, demeaned, denied, suspended, scapegoated, held back, pushed down or killed on account of the color of your skin. For 238 years, we have lurched in fits and starts toward fulfillment of that promise, periods of progress followed by periods of regress. We find ourselves in a latter such period now — mass incarceration rampant, the courts hostile, voting rights again under siege, black boys being killed for wearing hoodies and playing their music too loud.

The 50th anniversary of the Civil Rights Act is certainly a time for celebration and reflection. But let no one indulge the fantasy that we are “there” now and thus, may cease driving toward the fulfillment of America’s promise.

Kansas City is a great place to be. But it is many miles from Seattle.