Mary and Tammy received their legal training at major Houston, Texas law firms. Mary spent nine years at Butler & Binion, while Tammy worked for five years at Richie & Greenberg and Gilpin, Paxson & Bersch. After leaving their respective firms, Mary and Tammy collaborated on several probate litigation cases and found that their philosophies and working styles complemented each other.

     In 1997, Mary and Tammy formed their partnership and chose as their office a charming Victorian home built in 1912 and located close to downtown Houston, Texas. The law firm focuses on probate litigation (for example, will contests), estate planning, estate administration (probate), guardianship and general civil litigation. Given that many of the cases handled by Galligan & Manning involve estates and family relationships, the attorneys place a high priority on preserving family relations while resolving interfamily conflicts. Mary and Tammy are also trained mediators and offer a team mediation approach to contested probate matters.