One note, Postgres is well over 18 years old. Postgres using SQL is 18 years old. Postgres had its own query language which was replaced with SQL in Postgres95, which in turn became PostgreSQL.
PostgreSQL evolved from the Ingres project at the University of California, Berkeley. In 1982, the project leader, Michael Stonebraker, left Berkeley to make a proprietary version of Ingres. He returned to Berkeley in 1985 and started a post-Ingres project.
Starting in 1986, the team published a number of papers describing the basis of the system, and by 1988 had a prototype version. The team released version 1 to a small number of users in June 1989
