Members of the FBI's Joint terrorism Task Force arrested 50-year-old Karen Waller at her home in Irvington on Tuesday.
Prosecutors say Waller mailed more than 50 threatening letters in May and June to the court, Rutgers University, Woodbridge town hall, Milburn police and an insurance company. Authorities say the letters threatened to injure and kill unspecified people.
Waller is charged with one count of mailing threatening communications.
Waller is scheduled to make an initial appearance in federal court in Newark on Tuesday afternoon.