The former Child Advocate was tapped by Gov. Jon S. Corzine to lead the new Department of Children and Families in 2006.
Ryan is credited with leading a turnaround of the troubled child welfare system after officials were forced by court order to improve protection of the state's most vulnerable children.
"He took charge of a critically important program and we have made tremendous strides under his leadership," Corzine spokeswoman Lilo Stainton said.
Under Ryan, the number of adoptions and foster families increased dramatically, social workers' caseloads declined and training improved.
Independent monitors overseeing the multimillion-dollar reform effort have issued favorable progress reports. However, the ongoing effort will take years to complete.
"I think that there is still an enormous amount of work to do," Ryan said. "The good news is child welfare reform has taken hold in New Jersey. The adoption backlog has been halved, and records have been set for adoptions of foster children."
Ryan, a 41-year-old lawyer, is leaving at the end of February to do philanthropic work for the MCJ Amelior Foundation, an agency focused on improving the lives of at-risk children in Newark and Africa.
Ryan's chief of staff, Lisa Eisenbud, is also leaving - something that worries some child advocates.
"This is a very vulnerable time for there to be a change in leadership, and we are very concerned," said Marcia Robinson Lowry, executive director of Children's Rights, a New York-based advocacy group that sued New Jersey over claims the state wasn't doing enough to protect children in its care.
"I think a really good start has been made on the reform," Lowry said, "but it is far from being institutionalized."
