https://news.ycombinator.com/item?id=18427351

Design and manufacturing is in the los angeles region aerospace industry cluster.

It's been a US company for the last 13 years.

https://rocketlabcorp.com/updates/rocket-lab-makes-its-defen...

Design and manufacturing for the rocket part of their business is mainly split between Auckland and Los Angeles. Various sources say they have between 500 and 700 employees in NZ.

Earlier this year they acquired a new machining business in Auckland and are expanding capacity at their NZ launch site: https://rocketlabcorp.com/updates/rocket-lab-establishes-new...