Del. Hattie N. Harrison, the Maryland House of Delegates’ longest-serving member and one of the chamber’s pioneering African American lawmakers, died Monday evening. Harrison was 84.

News of Harrison’s death, announced on the floors of the House and Senate at the conclusion of the General Assembly’s 8 p.m. session, drew gasps from lawmakers.

“She guided us through many important moments,” said House Speaker Michael E. Busch (D-Anne Arundel). “She was affectionately known as our godmother . . . and she will be missed.”

Harrison (D-Baltimore) was first elected to the House in 1973. She ascended to chair the powerful House Rules and Executive Nominations Committee seven years later and held that post until recently. Harrison had been in hospice care in recent weeks. She had not been in the State House since the legislature reconvened on Jan. 9.

Her death leaves yet another seat to fill this year in the House. Last week, Gov. Martin O’Malley named former delegate Darren Swain to fill the vacancy left by the ouster of Del. Tiffany Alston.

After pausing for a moment of silence in Harrison’s honor, the House adjourned for the day. “Someone will come down here and take her seat,” Busch said, “but no one will ever take her place.”