The South End is recognized as the largest concentration of Victorian brick row houses in the country and was placed on the National Register of Historic Places in 1973.

One of the most anticipated events of the fall season is the South End Historical Society’s annual house tour. This year will mark its 50th tour. It will be held from 10 a.m. to 5 p.m. on Saturday, Oct. 20, rain or shine, and will showcase six incredible homes.

This event also is the society’s major fundraiser with proceeds earmarked for its programming throughout the year.

The South End is recognized as the largest concentration of Victorian brick row houses in the country and was placed on the National Register of Historic Places in 1973. Ten years later, the Boston landmarks Commission designated it as an historic district. (The area extends approximately from Herald Street to Camden Street and from the Southwest Corridor and Harrison Avenue. It was expanded beyond Massachusetts Avenue to include Northampton Street four years ago.)

But before that, even before the society was founded in 1966, there was a house tour. Doe Sprogis was a guiding light for all the tours until her death in 2015, said Lauren Prescott, executive director of the society. “The tour continues in her memory.”

This year will feature six unique properties, both single-family homes and condominiums. Two are in former churches that have been repurposed into luxury residences and one comprises an Airbnb, which is a standout.

Tickets are available in advance for $30 and can be purchased online at www.southendhistoricalsociety.org or by calling 617-536-4445.

Because these residences are within an historic district, the city does not allow any major exterior alteration in keeping with the distinctive fabric of the neighborhood. It is what lies behind the front doors that make this tour so captivating.

One property was featured on the tour several times and has undergone remarkable changes.

One of the tour houses, built in 1866, has been painstakingly restored to its Victorian grandeur. What could not be refinished was replicated in preserving the overall design. Elaborate crown molding and ceiling medallions glisten, and four fireplaces have been beautifully rebuilt for burning wood.

Another single-family house, built in 1880, has been transformed to modern living space. The garden level has a good-sized, informal living room, which opens out to a big garden and two parking spots, while the parlor level boasts a dining area with custom kitchen cabinetry and especially designed Italian furnishings. A nod to the house history is the stained glass set into the interior vestibule doors.

Both of the condos in former churches have retained a delightful detail of their former life, like a buttress or arched windows, but they do not overwhelm. One unit has exposed brick, painted white - all the better to display unique artwork. A stunning sunroom with a deck offers fabulous panoramic city views.

The other home, a triplex, has exposed stone incorporated into its stairway wall and an open living/dining room and stunning kitchen.

Just about all of these homes display unusual artwork, much of which has been acquired during travels. Some have custom-designed furniture that was made locally.

The sixth property on the house tour is the inn, which has four suites that will be on view. This house has evolved from a single-family house, to a lodging house, to three apartments to an innkeeper’s Airbnb.

Eclectic artwork abounds in each suite, which has exposed brick walls lined with shelves filled with books. Altogether, this property has five bedrooms and five-and-a-half baths.

Each kitchen is sleek with modern appliances, black counters and white lacquered cabinets, contrasting with the red exposed brick. The en suite baths are new.

The most dramatic characteristic in the Dartmouth Suite, however, is the 22-foot-high atrium that has French doors on the upper level that open to look down on the living space. A brass-and-chrome tree with twinkling lights soars 20 feet, and above it is the head of a cherub, presumably to serve as the angel.

According to the innkeeper, the tree is in place year round, but is redecorated for the holidays. This home also features a sky deck with outdoor tables and chairs and a sculpture set above a square of water with corner fountains.

Many of the other homes have outdoor spaces, too, such as patio gardens or decks, and home offices. All are interesting.

A South End house tour was first held in the early 1960s and was sponsored by the League of Women Voters. At the time, the city was undergoing urban renewal. Buildings in the New York Streets neighborhood were demolished in 1955, and three years later the West End was razed. More was planned.

There was a sense of urgency among new South End residents to stop the destruction, so several came together and founded the historical society, Prescott said. The society-organized tours began in the late 1960s and continue to today, now celebrating the neighborhood’s culture, diversity and vibrancy.

Tour day tickets will be $35 and may be purchased at Sprogis & Neale Real Estate, 679 Tremont St. Ticket holders will receive a keepsake booklet that includes descriptions of the homes and a map.

Visitors are free to follow the self-guided tour in any order. Food, drink, smoking, strollers and photography are not allowed inside the homes, and visitors should anticipate removing their shoes when they enter the homes.

Also available for sale will be tote bags and South End-related books. For more information, visit the website or call 617-536-4445.