(CNN) — Benjamin Todd Jealous will step down as president of the NAACP at the end of December, the civil rights organization announced Sunday.

“The NAACP has always been the largest civil rights organization in the streets, and today it is also the largest civil rights organization online, on mobile and at the ballot box too,” Jealous said in a statement issued by the group Sunday afternoon. “I am proud to leave the Association financially sound, sustainable, focused, and more powerful than ever.”

Jealous, 40, took the reins of the oldest and largest U.S. civil rights organization in 2008. In announcing his resignation, he said he wanted to spend “a lot more time with my young family” and work on training a new generation of civil rights leaders.

No successor was announced in the statement, in which NAACP board Chairman Roslyn Brock credited Jealous with building a staff able to “meet the civil rights challenges of the 21st century.”

During his tenure, Jealous was a prominent voice against laws the NAACP argued made it harder to vote, such as voter-ID laws passed in numerous states in the past several years. Recently, Jealous condemned as “outrageous” the Supreme Court’s decision to strike down a key portion of the 1965 Voting Rights Act and lobbied Congress to re-authorize the provisions that the court killed.

He advocated easing restrictions on voting by ex-felons; supported efforts to tighten regulations on gun sales after the massacre at a Connecticut elementary school in December; and was particularly outspoken over the February 2012 killing of Trayvon Martin, the Florida teen shot to death by a neighborhood watch volunteer.

Jealous called for the resignation of the police chief in Sanford, Florida, accusing him of mishandling the case by failing to arrest the volunteer, George Zimmerman.

Prosecutors eventually brought second-degree murder charges Zimmerman, who was acquitted in July. The NAACP has called for the federal government to charge Zimmerman with violating Martin’s civil rights after the acquittal, which Jealous said left the impression “that our young people have to fear the bad guys and the good guys — the robbers and the cops and the self-appointed community watch volunteer who thinks that they’re keeping folks safer.”