What is the voice of the verb in the sentence, "In 1492, Columbus sailed the ocean blue."?
This verb (and the whole sentence) is in Active Voice. See explanation.
In Active Voice sentence the subject is the doer of the action (the thing or person doing the action); here it is Columbus.
In the Passive Voice the subject is the thing upon which the action is done.
To see the difference let's compare two sentences:
John's parents built this house in 1960.
This house was built by John's parents in 1960
In the first sentence the subject is the person who actually did something: John's parents.
While in the second sentence the subject is a result of an action (the house). The doer is added here by an additional clause by John's parents