Two facts about the address decide whether a surprise stays a surprise here. The first is that 18966 is not one municipality: the ZIP covers Upper Southampton Township and reaches into the western edge of Northampton Township, while the neighborhoods people also call Southampton — Feasterville and Trevose, in Lower Southampton — carry 19053 instead. Two townships, two ZIPs, one name, and a driver who reads the ZIP. The second is that Pennsylvania reuses the name freely: there are Southampton townships out in Cumberland, Franklin, Bedford and Somerset counties, and the Southampton that search engines want to show the rest of the country is on Long Island. So write 18966 on the order, give the street, and add the development or building name if the house sits inside one of the townhome clusters off Street Road or Second Street Pike. That one line of care is the difference between a birthday bouquet on the right porch at noon and a phone call you did not want to make.
Riverside's 11.3 miles are worth a footnote, because the number is measured across the Delaware rather than along a road. Reaching Bucks County from Burlington County means the Tacony-Palmyra or the Burlington-Bristol bridge, so a Southampton birthday almost always routes to a Bucks or Montgomery bench even though a New Jersey shop looks close on the map. The same logic applies in reverse to anyone sending from out of state: the system picks by real routing, not by straight-line distance, and you do not have to guess which shop is sensible. What you do have to supply is the destination type. A house in Upper Southampton is a porch drop. An apartment in Feasterville or Bensalem is a locked lobby and a buzzer code. An office off Street Road is a lobby desk with a name on it. Those three jobs look nothing alike to the person doing them, and saying which one it is at checkout is worth more than any note about design.
Where Southampton birthdays actually go splits roughly in half between houses and workplaces. On the residential side it is the streets off Second Street Pike, Bristol Road, Davisville Road and Knowles Avenue, plus the Richboro, Churchville and Holland addresses across the Northampton Township line and the Feasterville and Trevose blocks below it. On the working side the grid is unusually dense for a township this size: the Street Road commercial strip runs east out of Southampton through Feasterville and into Bensalem, where it passes Parx Casino and the Neshaminy Mall trade area, and the US 1 business belt at the Neshaminy Interplex in Trevose puts several thousand desks within fifteen minutes of the 18966 line. North and west, the Warminster and Horsham business parks, the Willow Grove retail cluster and — ten miles up Route 611 and York Road — the Bucks County seat at Doylestown with the county offices and the courts. Campus birthdays run to Bucks County Community College on Swamp Road and Holy Family University's Newtown campus, to Delaware Valley University in Doylestown, and to Bryn Athyn College four miles southwest. High-school-age deliveries mean William Tennent in Warminster and Klinger Middle School in Southampton in the Centennial district, Council Rock South in Holland, Archbishop Wood in Warminster and Villa Joseph Marie in Holland.