Two institutions that have not only made major contributions to Durham but have helped to define the city's identity marked major milestones last week.

Both exemplify the rich heritage African-American institutions have in a diverse community where African Americans have constituted a prosperous middle and upper economic class unusual in Southeastern cities.

On Friday, N.C. Central University, embarking on a celebration of its centennial year, observed its annual convocation. Chancellor Charlie Nelms noted the impact the school's graduates have had on the community, on the state and in the world while focusing the institutions' attention on challenges and opportunities ahead.

Coincidentally, also on Friday N.C. Mutual Insurance Co. turned over its extensive and invaluable archives to NCCU and Duke University. The two universities -- which in another evocative coincidence would play their historic first football game against each other the next day -- will share guardianship of the archives and make them available to scholars.

James Speed, N.C. Mutual's president, reminded an audience at the official transfer on Friday that "the collection highlights the historic role the company has played both locally and nationally." And he said making the collection available will allow the universities to "show the world what North Carolina Mutual has meant to the world."

Duke President Richard Brodhead remarked on the impact NCCU and N.C. Mutual -- as well as his institution -- have had on the city. "The city is in some profound way the result of the collaboration of these three institutions," Brodhead said.

While Duke's growth and evolution into a top-tier university took brilliance and unstinting effort by generations of university leaders and benefactors, its road was not nearly as challenging as that of the other two institutions that for much of their distinguished history had to struggle against southern apartheid.

Friday was a day, however, not just for celebrating that past but for looking to the future, to how the story of N.C. Mutual's operations through the decades will help propel scholarly understanding of its success.

And, at N.C. Central, Nelms made clear, the successes of the past are only the prelude to the challenges of the future.

Going forward, he said, "anything less than excellence is unacceptable."

That commitment is an appropriate way of honoring the legacy of both historic institutions.