Forms in –st, such as whilst and amidst, are generally archaisms. Amongst is no exception: in American English it is best avoided.
“The question posed by this case has engendered division amongst
[read among] the commentators as well as a conflict amongst [read among] the courts of appeal.”
“The same rule also applied to a communication between members of a society pledged to maintain good morals amongst [read among] its adherents.” Amongst seems more common and even more tolerable in British English, where it carries no hint of affectation.
“The first count of the declaration stated that the plaintiff has contracted to perform in the theatre for a certain time, with a condition, amongst others, that she would not sing or use her talents elsewhere during the term without plaintiff’s consent in writing.”