Former Baltimore Mayor Catherine Pugh was indicted on federal wire-fraud and tax-related charges stemming from her self-published “Healthy Holly” children’s books, which were at the heart of a political scandal that prompted her resignation in May.

Ms. Pugh, 69 years old, resigned under pressure following revelations that she grossed more than $500,000 selling the books to companies, nonprofits and foundations, including some that benefited from her official actions. The Democratic politician was a long-serving state senator...