When Brooklyn became part of New York City in 1898, vast parts of the present borough had themselves only recently become part of the City of Brooklyn. Kings County comprised six towns, of which one, called Brooklyn, became a city in 1834. Another, Bushwick, joined Brooklyn in the 1850s. In 1894, three others, in agricultural areas of the county, joined: Flatbush, Gravesend, and New Utrecht. Flatlands joined in 1896.The latecomers remained little developed into the 20th century. In the 1920s and 1930s, they boomed.

New Utrecht comprised such present-day neighborhoods as Bay Ridge, Bensonhurst, and Dyker Heights. As throughout Brooklyn, neighborhood boundaries are hazy. Dyker Heights sits between Bay Ridge and Bensonhurst in southwestern Brooklyn. Its boundary with Bay Ridge became well-defined when the Gowanus Expressway was built. To the east, no one seems sure where Dyker ends and Bensonhurst begins. Still, Dyker Heights has a definable center, between 10th and 14th avenues, in the 1970s and 1980s. Every year at this time thousands of people flock to 83rd and 84th streets between 10th and 13th avenues. Why? To gawk at Christmas decorations on houses.

For 75 years Dyker Heights has been a middle- and upper-middleclass Italian-American neighborhood. Early on, it’s where Italians settled who had made successes of themselves. Many of Dyker’s commodious, freestanding houses are quite lovely. Subsequent generations of Italian-Americans stayed on, defying sociologists’ expectations of ethnic succession. Lately, the Italian presence has eroded somewhat, as nice old houses yield in places to those peculiar urban variants of suburban “McMansions” that are sprouting all over Brooklyn. Amid such changes, it’s sad to report that the Christmas extravaganza probably peaked some years ago, though it still astonishes.

Italians have a festive impulse, having, for example, introduced street fairs to New York. Some houses here bear thousands of electric lights as well as motorized vignettes of holiday scenes replete with piped-in music. The Polizzotto family house, an imposing mansion with a columned and pedimented porch, at 1145 84th St., is the reigning Queen of Dyker Heights. A giant Santa figure, Nutcracker soldiers, and lighted Christmas trees festoon a house in what is, in fact, a scaled-down version of years past.

This block, between 11th and 12th avenues, gets the most visitors. But walk around the neighborhood. Many smaller displays that visitors overlook can be quite lovely. I strolled Dyker on a chilly night recently equipped with a hot chocolate from Mona Lisa, a cafe at Fifteenth Avenue and 86th. I passed by the big Knights of Columbus hall at 13th Avenue, where their annual Christmas disco party swung into the night.

Around the corner, at 83rd Street, stands the National Shrine of St. Bernadette, built in 1937. Henry V. Murphy, one of New York’s most underrated architects, designed this gem, which ranks among the best modern churches in New York. Its garden sculpture of the grotto at Lourdes defines the neighborhood: It flirts with kitsch, then teasingly pulls back to show the essential dignity of this Italian-American enclave.