Selecting table row with latest date

I have a table of contacts (PK is the person_nbr and contact_date) and I
want to select only the row with the latest (most recent) contact_date. The
Comparison Date/Time sections in the postgres 12 doc doesn't appear to have
what I want, and when I try to use the max() aggregate function it throws an
error.

Please point me to the proper place in the docs where I can learn how to do
this.

Rich