Massachusetts Gov. Deval Patrick made history today when he announced the appointment of William "Mo" Cowan as his state's new interim U.S. senator to fill the vacancy left by the departure of Sen. John Kerry to be secretary of state.

Cowan will join recently appointed Sen. Tim Scott of South Carolina, making this the first time in history when America has had two Black senators serving at the same time.

That sounds like progress, and in many ways it is, but let's also remember how long it took to get this far and how far we still have to go.

Only four states — Mississippi, Massachusetts, Illinois, and South Carolina — have sent Blacks to the Senate. Forty-six others have never elected or even appointed an African-American to that post.

Massachusetts ranks as one of the most progressive states in the country. It's one of only four states in history to be run by a Black governor and it was responsible for electing the first African-American to the United States Senate — Edward Brooke in 1966 — in the modern era. Brooke, a moderate Republican, also holds the distinction as the only Black senator in U.S. history ever to be re-elected to office.

Only Mississippi and Illinois have better records. The Land of Lincoln has given us three Black senators: Carol Moseley Braun, Barack Obama and Roland Burris. And Mississippi? The first two Black senators, Hiram Revels and Blanche K. Bruce, both of Mississippi, served from 1870 to 1881, during the post-Civil War Reconstruction era. But then for the next 86 years, during the era of segregation and most of the civil rights movement, there were no African-Americans in the U.S. Senate. None.

That's why we need to put Cowan's appointment in perspective. Cowan will be the 1,946th person ever to serve in the U.S. Senate and only the eighth African-American to do so. That means less than one half of one percent (.411 percent to be precise) of all U.S. senators in American history have been Black. And 63 percent of those senators came in just the last 20 years.

To give you an idea of how recent this phenomenon is, consider this. Of the eight African-Americans to serve in the U.S. Senate in our history, six of the them are still alive.

Why does the Senate matter? The Senate is the only body with the power to ratify treaties, confirm appointments to the Supreme Court and remove the president from office.

When the U.S. Supreme Court decided landmark civil rights cases such as Brown v. Board of Education and Loving v. Virginia, they did so with court members who were appointed by white presidents and confirmed by white senators. And when President Kennedy appointed Thurgood Marshall to the United States Court of Appeals for the Second Circuit in 1961, a group of white southern senators held up his confirmation, forcing Kennedy to place Marshall on the bench through a recess appointment.

Yes, we now have two Blacks serving in the Senate. But that's 2 percent in a country where Blacks make up 12 percent. And neither one of them was elected to that office. Both were appointed by their state governors.

Yes, also, we've made progress as a nation. Last week we celebrated the second inauguration of the nation's first Black president. But real sustainable progress will require us to plant the seeds for more Black elected officials to follow in the footsteps of the few who now hold office.

So today, nearly 50 years after the landmark 1964 Civil Right Act, we have reason to celebrate. But we still have a long way to go.

Keith Boykin is a New York Times best-selling author and former White House aide to President Clinton. He attended Harvard Law School with President Barack Obama and currently serves as a TV political commentator. He writes political commentary for BET.com each week.

The opinions expressed here do not necessarily reflect those of BET Networks.

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