In England, Ostara (it has many other spellings) has been celebrated sine the time the first Saxons came here.It was, of course, "adapted" by Christianity as Easter by the 7th century. But it is still very much "alive" in parts of England.
It is the time of "rebirth",when the Earth "blooms", the coming of the "true light" of Spring.It is he time when Hares become very active.(So active that we still refer to "the mad March Hare!) In old times, it was thought that Hares laid eggs; so we now have all sorts of "eggs" at this time. Children paint eggs,there are ceremonies of "rolling eggs", and the shops are full of chocolate eggs!
So, to celebrate Ostara, Spring flowers, eggs, model of a Hare, (It is where the Easter bunny comes from!). In the North of England there are bonfires in the countryside, when all the old "lumber" is burnt. It was, and still is in most of England, a "fertility " celebration.Many couples choose to get married at this time of year.
It is really all about the "re-birth" of Spring; and probably also is the USA.
So, the origins of Ostara come from the European settlers in England,Saxons, Angles, Jutes, and Vikings. But, even before these,the Celts celebrated "Springtime".