Sweating and dirt-smudged, Joe Bagley stands smiling over relics plucked from a long-forgotten privy beside the Old North Church. To him, they are buried treasure: broken dinner plates, bottles, marbles, dolls, and dice.

Bagley is the city’s archeologist, and this is no ordinary privy. The 7-foot-deep hole off Salem Street has unveiled day-to-day details of 19th-century life in the congested North End like few discoveries before it.

“We have an unbelievable opportunity here to see snapshots of the immigrant story,’’ Bagley said last week.

Bagley and his volunteers have found those snapshots among well-defined layers of trash from about 1830 to 1890. The most recent artifacts lie near the top, the oldest near the bottom, in a pit that the household used for trash disposal as well as its sanitary needs.

It’s a time capsule from 2 Unity Court, wedged off a short and narrow street, that shows how the fortunes of its families slipped over the 19th century. From respectable English dinnerware at the beginning, to cheap plates at the end, the quality of life declined in a three-story brick building that measured 32 feet long by 14 feet wide.

“Archeology is the study of human trash over time, so you go where the trash is,’’ Bagley said. “You get the raw history here, good and bad.’’

That history is being unearthed because of plans by the Old North Church to remake an adjacent courtyard — now called Washington Memorial Garden — into an outdoor classroom for school groups and other visitors to the Revolutionary War landmark.

Before that renovation can begin, the site has been probed for artifacts of historical significance. Bagley and a platoon of volunteers furnished the inexpensive labor, using shovels and trowels to dig at the site this summer.

“We are essentially blowing up this garden to rebuild it,’’ said the Rev. Stephen T. Ayres, the Episcopal vicar of Old North Church. “I told Joe: Go at it; make a mess.’’

Bagley has done just that. Sprawling piles of dark-colored dirt were stacked over much of the 42-square-foot courtyard, where a crabapple tree rises from the middle. Clear bags filled with thousands of pieces of 19th-century trash were arranged neatly in a corner.

At the western edge of the courtyard, tucked behind buildings that face Salem Street, a series of trenches and pits uncovered the history-rich privy and a massive, rain-collecting cistern. The holes were being refilled last week.

The crew initially found the cistern, which did not hold much interesting material, Bagley said. Later, a few feet away, the privy was discovered in a “eureka’’ moment.

Few sites have been excavated from that period in the city’s history, when New England was transitioning to an industrial economy, according to Mary Beaudry, chairwoman of the archeology department at Boston University.

The finds could make a “wonderful contribution to what we know of Boston as an emerging metropolis and what life was like for its residents — be they long-resident Yankees, newly arrived immigrants, or folks from rural New England seeking employment or a better life in the city,’’ Beaudry said.

That contribution will come from the privy at 2 Unity Court. Lyman Locke, for example, lived there from 1835 to 1843 and appears to have enjoyed at least a few middle-class comforts, judging by the English ceramics that Bagley examined.

Locke is listed in city records as working a “balance,’’ which would have weighed important, everyday commodities, possibly at nearby Haymarket.

By the last quarter of the century, however, the crockery had become inferior. Irish immigrants appear to have moved in, Bagley said, and the building probably had been divided into apartments that housed blue-collar workers such as the laborers and seamen who swarmed through the crowded neighborhood.

A pipe decorated with a shamrock is among the later finds. “The people who were living here fought so hard for what they had,’’ Bagley said.

There also are cups, a glass oil lamp, and a clear vial for pills dispensed by W.T. Conway, a Boston chemist. If old advertisements for Conway’s products are any indication, whoever bought that “medicine’’ probably was in pain.

Conway wrote in one ad that “Dr. Relfe’s Botanical Drops,’’ which he prepared, had cured Hanover Street resident Sargent Rogers, who had been “severely afflicted with an eruption for 15 years all over the head, hands, legs, arms . . . often times forming a solid crust as thick as a dollar.’’

Ayres, the Old North vicar, said the church has an obligation to help tell the area’s long history. So much of Old North’s story has been confined to one night — April 18, 1775, when its two lanterns signaled the British were coming — that the saga of its neighbors has been obscured.

“This is part of our mission,’’ Ayres said.

To illuminate that story, the artifacts will be available for public study at the city’s archeology lab in West Roxbury. But first, they will be washed, sorted, photographed, and rebagged in a tedious, painstaking job to protect the past for the future.

Charles Deknatel, a 72-year-old volunteer from Jamaica Plain, has been part of the effort. Last week, he slowly tossed shovels of dirt back into the privy. Thousands of clues about 19th-century Boston had been discovered and retrieved, and now it was time to go.

“There has to be an end point,’’ Deknatel said. “It can’t go on forever.’’

But, in some ways, that is what has happened. Long-discarded clues to Boston’s history have been saved for generations to come.

Brian MacQuarrie can be reached at brian.macquarrie@ globe.com.