D defs.my
Entry 1 sense Webster, 1913

Whereupon

/wĕr'-əp-än'/ · Where·up·on · IPA /ˌ(h)wɛrəˈpɑn/
01 adv. Upon which; in consequence of which; after which.
  1. 1.
    Upon which; in consequence of which; after which.
    “The townsmen mutinied and sent to Essex; whereupon he came thither.” Clarendon.