Alyssa Park is a mentioned-only character in Fallout 4.
Alyssa was the mayor of the town of Jamaica Plain until October 23, 2077, the day the bombs fell. Prior to this, she spent a large amount of time on her pet project "Treasures of Jamaica Plain." Diverting much of the funding meant to be going to the town hall's basement maintenance, the exhibit was built in the town hall basement itself as a sort of time capsule for future generations. The project caused the town to exceed its budget by $12.23 million, causing the building janitor to speculate about calls for impeachment. The bombs falling made this a non-issue, however.
Alyssa may also be heard on the holotape The Treasures of Jamaica Plain.
Alyssa Park is only mentioned in Fallout 4.