Was????

It would be "estaba" or "era", the same as es and esta

Depending of if it was temporary like
"i was happy"
Estaba feliz

"they were happy"

Estaban Feliz.

 

There are two verbs in spanish that translate as "to be" in english: "Ser" and "Estar".

"Ser" implies a relative permanence "Yo soy peruano" (I am peruvian). "Estar" implies a temporary quality "Yo estoy enamorado" (I am in love). "Estar" also is used to specify a location "Yo estoy en el aeropuerto" (I am at the airport), you never use "ser" to indicate location.

In your example (being happy), you can use both ways. "Antes de casarme yo era feliz" (Before marrying I was happy) or "Yo estaba feliz ayer por el resultado del juego cuando..." (I was happy yesterday about the outcome of the game when...)

So, the past tense of "ser feliz" is:
-Yo era feliz
-Tú eras (Usted era) feliz
- El (ella) era feliz
- Nosotros éramos felices
- Ustedes eran felices
- Ellos (ellas) eran felices

And the past tense of "estar feliz" is:
-Yo estaba feliz
-Tú estabas (Usted estaba) feliz
-El (ella) estaba feliz
-Nosotros estábamos felices
-Ustedes estaban felices
-Ellos (ellas) estaban felices

It is much more complicated than just that and very difficult to explain, you just know when to use "ser" and when to use "estar". On the other hand, having 0nly one verb in english, there are some times I feel I cannot convey the right meaning of mi words, at least not as accurately as I do in spanish.