PPST is officially incorporated under the name Planned Parenthood of Chemung County - Corning, Inc. on December 23, 1968, opening offices in Elmira and Corning, the birthplace of Margaret Sanger!
- 1970 - Churches donate space so that Planned Parenthood can offer services to the Hornell community.
- 1972 - Patient numbers jump from 103 in 1969 to 2,345 in 1972. Planned Parenthood of Chemung County - Corning, Inc. changes its name to Planned Parenthood of the Southern Tier, Inc.
- 1973 - Five clinic sites are operating. Centers in Elmira and Corning are open full time, and the remainder are mobile units traveling to rural areas.
- 1985 - PPST starts a pre-natal program, successfully serving women for several years.
- 1986 - PPST opens the current Hornell office.
- 1988 - PPST starts confidential HIV testing.
- 1991 - With generous support from donors, PPST opens its Margaret Sanger-Katherine Houghton Hepburn Clinic in Corning.
- 1996 - PPST begins offering services as Rape Crisis of the Southern Tier. In the same year, PPST becomes the lead agency for the Community Based Adolescent Pregnancy Prevention Program of Chemung County.
- 1999 - PPST's current Elmira center opens.