Long Island, that strange place jutting east from New York City for 100 miles, was once the very symbol of America’s postwar future, of youth and growth, and is now the opposite of that. It is an old suburb that ran out of places to sprawl, was badly hit by recession a decade ago and again in the latest downturn, and is feeling its age.

Many of Long Island’s leaders have warned that it is heading steadily down a long, slow road to ruin. It needs more jobs, cheaper housing, better transit, economic engines to replace the ones that sputtered out. It needs its vitality back.

These were the heavy bass notes of what was generally an upbeat meeting of influential Long Islanders on Tuesday at Molloy College in Rockville Centre. It was sponsored by the Long Island Index, a nonprofit organization that issues annual reports on ways the Island can better itself. This year’s report was on mass transit, specifically increasing the capacity and usefulness of the Long Island Rail Road, the sprawling passenger network that hasn’t grown significantly in, oh, a century and a half.

Walt Whitman, Long Island’s most famous son, was still a nobody in Brooklyn when the L.I.R.R. completed its main line across the Island in 1844. The village at the eastern end, Greenport, was heavily into shipbuilding and whaling. A lot has changed since then, notably the growth of the island’s population to 2.8 million. But one part of the island — a troublesome, 10-mile section of the L.I.R.R. between Floral Park and Hicksville in Nassau County — still lives in the 19th century. It has two tracks, and only two, making it a perennial cause of congestion and delays. Five of the railroad’s branch lines — and 41 percent of its ridership — converge there. This bottleneck can be a disaster in bad weather; it also keeps the railroad from sending more trains east from Penn Station, against the regular commuter flow, out to where many jobs are, or could be.