The past progressive is most useful when

when an action happened in the past
when an action was uninterrupted in the past
when an uninterrupted action happens
when an action gets increasingly common

When an action gets increasingly common.

Explanation:

The past progressive verb form illustrates an action that was in continuity or progress in the past. It displays the several actions like actions of the past that were interrupted, the two actions happened simultaneously, an action taking place when another happened but it would best describe the action when it gets increasingly common. For example, "He was drafting a letter when I reached there" or 'They were cooking dinner and I was watching T.V. effortlessly'. These two statements best illustrate the increasingly ongoing actions of the past that are "writing", "cooking", "watching" which were in progression at that time.

in 1636, roger williams settled at the tip of narragansett bay after being banished from the massachusetts bay colony for his religious views, on land granted to him by the narragansett tribe. he called the site "providence plantation" and declared it a place of religious freedom.

explanation: