In 1992, Herb became Head of the Education and Behavioral Sciences Library at Penn State. Six years later, he was appointed Affiliate Professor of Language and Literacy Education in the College of Education. In these positions, he advised and mentored more than thirty students through internships and thesis projects. His first-year seminar course (LST 101T: “Stories and Storytelling: How Humans Became People”) resulted in his naming as Penn State’s Most Innovative Faculty Member in 2000 by the Penn State Schreyer Institute for Innovation in Learning and the Penn State Undergraduate Student Government Academic Assembly—a rare achievement for a librarian. The same year, he won the University Libraries award, the highest award for library employees at Penn State. From 2007 to 2009, Herb was also a visiting professor in Library and Information Science at Dominican University in Chicago. During his Penn State years, Steven and Sara Willoughby-Herb published works that provided a research base for their work in early and family literacy, including two textbooks, Using Children's Books in Preschool Settings (1994) and Connecting Fathers, Children, and Reading (2002), both produced by Neal-Schuman. Herb authored or co-authored more than 100 other articles, book chapters, presentations, and speeches over the course of his career.  

From the 1990s through the 2010s, Herb had national influence on the practice of children’s librarianship. He served on numerous committees within ALA’s Association for Library Service to Children (ALSC), including a term as President (1995-1996). He also served as Chair (1997-2001) of ALA’s Intellectual Freedom Committee, a group that monitored and countered censorship efforts in libraries. Children’s librarianship and intellectual freedom were closely-related areas during this time as the Internet became increasingly available to the general public and there were concerns about children’s access to sexual, violent, and other "adult" materials. Herb believed that encouraging children to use technology was just the latest extension of librarians’ traditional role in encouraging kids to enjoy books. Importantly, he advocated that young people should have the freedom “to explore what has meaning for them.” As ALSC President, he further wrote that "just as children should be able to find themselves—their face, their family, their dreams—on the shelves of a library, they should also be able to find the answers to their questions in more than one format" (Herb, "President’s Message"). Thus, he frequently opposed or raised concerns about curbing children’s access to online information. This was and remains a courageous stance, given that public and school libraries have been frequent sites of censorship, and that the Children’s Internet Protection Act, passed in 2000, ultimately required most educational institutions to filter obscene content.  

Another area where Herb had significant influence was in national children’s literature awards. For example, in 2012 he chaired ALA’s (Randolph) Caldecott Award Selection Committee. During his career he also served on ALA's (John) Newbery Award Selection Committee and (Theodor Seuss) Geisel Award Selection Committee. By identifying and vetting works to receive these prestigious awards, Herb and other librarians shaped purchasing decisions in thousands of libraries nationwide.  

While active on the national level, Herb also engaged in various projects to promote literacy in his home state of Pennsylvania. He began early this work early, with the establishment of the Children's Literature Council of Pennsylvania (1985-1998) and its publication, the Journal of the Children's Literature Council of Pennsylvania. In 2000, he instigated the move of the Pennsylvania Center to the Book from the State Library of Pennsylvania to Penn State University Libraries and became PACFTB’s Director. In a 2021 interview, Herb recounted four promises he made to himself regarding the center’s work: 

As Director of PACFTB, the Literary and Cultural Heritage Maps of Pennsylvania, a biographical and information resource used by educators, students, and the general public, was one of the earlier initiatives Herb developed. Launched in 2000, before Wikipedia and many other digital humanities projects existed, the Maps project was the recipient of the Library of Congress’s Boorstin Award for Creative Initiatives (2005) and expanded to include hundreds of biographies and feature articles. In 2011, Herb also created the Lynd Ward Graphic Novel Prize to recognize a pioneering artist in that genre. In addition, he began to shepherd the Lee Bennett Hopkins Children’s Poetry Award, which annually recognizes the best children’s poetry works. This collaboration with Hopkins, a prolific anthologist of children’s poetry, resulted in a lasting friendship. 

In 2018, ALSC awarded Herb its Distinguished Service Award in recognition of his sustained leadership in the association, noting that he served the organization for thirty-five years in twenty-five different positions. His many contributions demonstrated his devotion to championing children’s and family literacy and his belief in the significance and impact of national service to professional organizations.