Charles K. Landis was not a stranger to building towns from nothing. He had already founded Vineland, New Jersey, an inland farming community organized around progressive principles - temperance, the family farm, the planned street grid. Sea Isle was his coastal counterpart, designed for summer leisure rather than agricultural work. The main street, Landis Avenue, still runs the length of the island. The oldest surviving building from his era is the Colonnade Inn, a Victorian-era hotel that opened in the 1880s and continues to operate as a small inn. Most of the rest of Landis's original architecture has been lost to storms and tear-downs. The grid he laid out, though, is intact, and Landis Avenue still runs from Strathmere in the north end of Ludlam Island to the Townsend's Inlet bridge at the south.

Italian fishermen and their families settled the back-bay docks of Sea Isle City in the late nineteenth century. They built shanties on pilings over the marsh, lined up boats along the canals that Landis had partly cut, and turned the area into the closest thing to a Venetian working waterfront on the East Coast. The neighborhood became known as Fish Alley. Multi-generational Italian-American families still own the docks, still run the boats, and still operate dockside seafood restaurants supplied directly from their own catch. The fishery has shifted over the decades from the bay's once-rich oyster beds to commercial sport fishing and clamming, but the cultural continuity has held. Few small Jersey Shore towns retain anything like Fish Alley. The land values say the developers would gladly tear it down, and they haven't been able to.

On March 6, 1962, the Ash Wednesday Storm sat off the Jersey coast for five consecutive high tides. Sea Isle City was nearly destroyed. Three days of continuous rain combined with onshore winds and astronomical tides put nearly every beachfront property under water. The causeway flooded, cutting the island off from the mainland, and the final evacuations were carried out by helicopter. When the storm cleared, residents came back to find foundations swept away, roofs gone, contents scattered across the marsh. The rebuilding that followed reorganized the town. A new dune line was established, and beachfront construction was pushed back roughly one full block from the previous shoreline. The dune line saved Sea Isle City from later storms. It is the geological scar of the 1962 storm, still visible from the air.

Sea Isle City's marketing campaigns lean into the family-friendly summer angle. The Sara the Turtle Festival, named for a fictional diamondback terrapin meant to teach children about the local environment, runs each summer with face painting and live animal exhibits. The Polar Bear Plunge each February is genuinely older and stranger - by 2019 it had reached its twenty-fifth year, and the participants now include large numbers of costumed swimmers running into the Atlantic surf at temperatures most boats would refuse. The town's signature water tower has slowly shed words. It used to read "Welcome to Sea Isle City." In 2002 it became "Smile! You're in Sea Isle City." In 2018 the word "City" was dropped. The current message reads, simply, "Smile! You're in Sea Isle."

There is a stranger footnote to Sea Isle City's history. In 1987 the US government reflagged a Kuwaiti oil tanker under the United States flag and renamed it MV Sea Isle City - part of Operation Earnest Will, the US Navy effort to protect oil shipping in the Persian Gulf from Iranian attacks during the Iran-Iraq War. On October 16, 1987, an Iranian-fired Silkworm missile struck the Sea Isle City off the Kuwaiti coast, wounding eighteen crew members and seriously damaging the ship. The United States responded with Operation Nimble Archer, destroying two Iranian oil platforms in retaliation. A tanker named for a New Jersey resort town had become a flashpoint in a war eight thousand miles away. The crew survived. The ship was eventually repaired and put back into service. The strangeness of the story has not entirely faded.