Union City is a little over a square mile on the Palisades bluff above Hoboken, and one of the most densely populated cities in the United States — roughly seventy thousand people on a grid of walk-ups, two-families and storefronts that runs from the Weehawken line to North Bergen. Bergenline Avenue is the commercial spine, with John F. Kennedy Boulevard, Summit Avenue and Palisade Avenue carrying the rest of the traffic and Washington Park anchoring the Jersey City end. It is a city with a strong Cuban and Latin American character, a long embroidery-trade history, and the Park Performing Arts Center on 32nd Street still hosting the productions the neighborhood grew up with. All of it sits inside a single ZIP: 07087.
That one-ZIP compactness makes addressing the main thing to get right. Union City was formed from two older townships, Union Hill and West Hoboken, and both names survive in family directions, older records and long-standing business listings. They are worth keeping in the card or the notes if that is how your recipient talks about their block — but "West Hoboken" is not the present City of Hoboken, which is a separate municipality down at the bottom of the bluff, and an order addressed that way can be routed a mile and a whole city off target. Put Union City and the current street information on the delivery, and let the historic name live in the message.
Two local details are worth settling before you check out. If the gift is a school thank-you, the address on file — Union Hill Middle School's 3808 Hudson Avenue, for instance — gets a courier to the door but grants nothing beyond it, so ask the office how a personal gift should be received and choose something the recipient can take home. If it is sympathy, work from the family's current notice rather than a saved contact: Leber Funeral Home's own page, reached from its former Union City URL, now lists a Secaucus address, and the receiving location for a particular service has to be confirmed before a tribute is ordered. And whatever the occasion, write the card in the language you actually share with the recipient, then read the preview for names and accents before it prints.