Descendents of Peter and Elizabeth Clark--Jefferson or Wapello Counties, Iowa,

Looking for Descendents of Peter and Elizabeth (Eliza) Clark.They were living in Jefferson County, Iowa (Fairfield?) in 1860 census.Census lists five children:
Anna (14); Bridget (11); Tom (3); Dennis (2); Kate (9 months).Believe one more daughter, Dora, was born later.
Census lists Peter as 31 and Elizabeth as 35.

Little more is known of Peter.It is believed he married Elizabeth prior to 1857.

Elizabeth was married previously to a man whose first name is unknown, but whose last name was Cavenaugh.Believe Elizabeth was born in Queens (or Laois) County, Ireland around 1825.First husband emigrated to U.S.May have died of yellow fever in New Orleans.Elizabeth and two daughters (Anna and Bridget)arrived later in U.S. in 1850.Subsequently married Peter Clark.It is unknown whether Peter adopted Anna and Bridget as they were known as both "Cavenaugh" and "Clark" as various times.

May have moved from Jefferson County (Iowa) to Wapello County (Iowa) after 1870.

I am related to Elizabeth through her first daughter, Anna Cavenaugh (Clark).