Port, of St. Louis, beat Toni Wiesner, 1-up, in the morning quarterfinals at the Eugene Country Club and needed four extra holes to eliminate Lisa Desimone in the semifinals.
The 41-year-old Port, a high school teacher and field hockey coach, won this title in 1995, '96 and 2000. She will face Kathy Hartwiger in Thursday's 18-hole final.
Hartwiger, a three-time Alabama state champion who works part-time for the U.S. Golf Association, cruised to a 7-and-5 win over Lyn Nelson in the semis after a 5-and-3 triumph over Susan Romano in the quarters.
Port is trying to surpass Sarah LeBrun-Ingram for the most titles in this event. LeBrun-Ingram won in 1991, '93 and '94.
'I feel like I'm a better player now than when I won my other three,' Port said. 'I knew I could get to the final, but you try not to think about it. So many things have to go your way.'
This is the 16th Mid-Amateur, a championship for women 25 and older who have a USGA Handicap Index not exceeding 9.4. The Women's Mid-Amateur is one of 13 national championships conducted annually by the U.S. Golf Association, 10 of which are strictly for amateurs.