I have json file exported from mongodb which looks like:
{\"_id\":\"99919\",\"city\":\"THORNE BAY\"} {\"_id\":\"99921\",\"city\":\"CRAIG\"} {\"_id\":\"99922\
Assuming you don't care about the exact filenames, if you want to split input into multiple files, just use split.
jq -c . < cities.json | split -l 1 --additional-suffix=.json - .chunks/cities_