They are one of Silicon Valley’s most prominent power couples. He is the co-founder of Slack, the messaging app that has helped redefine workplace communication and that was acquired by Salesforce in July 2021 for $27.7 billion. She is the co-founder and chief executive of Away, the trendy luggage manufacturer and retailer that was valued at $1.4 billion in a funding round in 2019.

Now, Stewart Butterfield and Jen Rubio are developing a reputation outside of Silicon Valley circles—as collectors of trophy homes.

Over the last two years, the couple has accumulated a portfolio of real estate that rivals those of some of the county’s most active billionaire home buyers. Their rapid spending spree, resulting in the purchase of at least five pricey homes between January 2021 and August 2022, spans at least three states and includes two downtown Manhattan properties, a Hamptons mansion, a mountain home in Aspen and a Tadao Ando-designed ranch in New Mexico. Since January 2021, they have spent at least $140 million.

Mr. Butterfield and Ms. Rubio did not respond to requests for comment, but real-estate experts said their properties are some of the most luxurious in their respective markets and represent a diverse range of styles and architecture.

Mr. Butterfield founded Slack in 2009. He stayed on as chief executive of Slack after it was acquired by Salesforce, but left the company entirely in early 2023. Ms. Rubio co-founded Away in 2015. The couple married in 2020, after a tongue-in-cheek proposal by Mr. Butterfield on Twitter the prior year. They share two young children. In 2021, Ms. Rubio described their family on Twitter as a “dual-founder household.”

Here is a closer look at their portfolio.

New Mexico

In January 2021, Mr. Butterfield and Ms. Rubio purchased an elaborate New Mexico ranch from fashion designer Tom Ford, according to people familiar with the situation. While the closing price wasn’t public—New Mexico is a nondisclosure state—market insiders said the eventual price was in the $40 million range, significantly less than the $75 million the property originally asked when it came on the market in 2016.

Known as the Cerro Pelon Ranch, the roughly 20,000-acre property is located in the Galisteo Basin area near Santa Fe and includes a main house and horse facility, both designed by Pritzker Prize-winning architect Tadao Ando, as well as Silverado Movie Town, an Old West whistle stop constructed in the 1980s as a shooting location for the movie “Silverado,” starring Kevin Costner, Danny Glover and Kevin Kline. Silverado Movie Town was later featured in “All the Pretty Horses” and “Thor.”

The main house, designed in concrete as per Mr. Andao’s usual style, sits above a reflecting pool. The property also includes four separate staff quarters and two private guesthouses.

Mr. Ford told The Wall Street Journal in 2009 that the ranch was a refuge for him. “We live in an artificial world. In the fashion business, you live in the future for the next collection. But when I spend time on my ranch in New Mexico—with the sun above me and the rattlesnakes growing under the bush—I appreciate the present,” he said.

“There are a lot of fabulous ranches in New Mexico, but this is the crown jewel,” said Kevin Bobolsky, the agent who listed the property. “You’re sitting in the high desert and, for as far as the eye can see, you don’t see another building. And you’re floating on a reflecting pool, almost like you’re in a boat.”

Mr. Bobolsky declined to comment on the buyers or the final price, but noted that there had been international demand for the ranch. “From Europe, Russia, all over the world,” he said. Clayton Orrigo of Compass represented the buyer alongside local agent Neil Lyon of Sotheby’s International Realty.

The Hamptons

In May 2022, Mr. Butterfield and Ms. Rubio paid $32.2 million for a historic gabled brick home in Southampton, N.Y., designed by architect Grosvenor Atterbury, who was known for designing homes for John D. Rockefeller Jr., as well as the American Wing of the Metropolitan Museum of Art.

The seller was real-estate developer David Walentas, widely recognized as the developer of much of Brooklyn’s Dumbo neighborhood, who said he spent two years and roughly $10 million renovating it. Mr. Walentas and his late wife, Jane Walentas, paid $11.6 million for the circa-1910 house in 2019 and he listed it for $35 million in April 2021, records show.

Sitting on about 3 acres, the roughly 17,000-square-foot home was configured with 11 bedrooms. The property blends intimate spaces with large ones geared for entertainment, according to the listing. South-facing french doors lead out to brick patios as well as a pool and pool house. The house is also surrounded by mature trees and flower gardens.

“The property’s location was awesome, so close to the beach,” said Cody Vichinsky, whose firm Bespoke Real Estate represented Mr. Walentas in the deal. “And the house felt old world but new at the same time with contemporary features.”

He said it was perfect for a buyer with “sophisticated architectural tastes.” He said Mr. Butterfield and Ms. Rubio were looking for “character” in a home. “They thought it was very handsome,” he said, noting that the deal closed quickly.

The deal was a pricey one for the Hamptons market last year, though it didn’t come close to breaking any price records. Still, “more than $30 million is nothing to sneeze at,” in the Hamptons, Mr. Vichinsky said.

New York City

In recent years, the couple have purchased at least two significant properties in New York.

They purchased the first, a rare 36-foot-wide townhouse in the West Village, for $27.27 million in August 2021, according to property records and people familiar with the situation.

Located on a quiet block near the Hudson River, the property, formerly owned by Australian designer Richard Tyler, has an unassuming 19th-century Romanesque brick facade that conceals a more upscale contemporary space behind. While it is unclear if the home has since been updated, an old listing describes large-scale entertaining rooms with 20-foot ceilings, a pavilion with a reflecting pool, ivy-covered walls and a retractable roof that opens to the sky. The property spans around 8,000 square feet, according to the old listing. All floors are Appalachian granite and have radiant heat.

In August 2022, the couple also bought a historic townhouse on a cobblestone street in New York’s Tribeca neighborhood, which came with exclusive use of a widely recognized and photographed skybridge. The price: $20 million. That was less than half the $50 million asking price when the property first hit the market in 2015.

At the time, the couple’s agent, Mr. Orrigo of Compass, said the property would serve as an office and programming space for the couple’s foundation.

The unique property includes a loft space in one building, which connects via the private footbridge to a separate four-story mansion with a garage and roof deck. Altogether, the property spans roughly 8,200 square feet with about 1,200 square feet of outdoor space. It was once home to the studio and private residence of fashion designer Zoran Ladicorbic, records show.

Local agent Andrew Azoulay of Douglas Elliman, who had been in the property, said that, thanks to the bridge, the building is “the most iconic site that there is.” It likely took so long to sell, and traded at such a significant discount to ask, because of its “quirky layout,” he said. He said he always thought the unit would be the perfect headquarters for a boutique hedge fund, so that the chief executive could have a private office on one side of the skybridge and employees could have their offices on the other side.

He said that, at the time that it was sold, the property was in need of major renovations, estimating the cost at at least $10 million. Mr. Ladicorbic lived sparsely in the unit. One room only had a single chair in it, Mr. Azoulay said. Another room was used for showcasing his designs.

“It didn’t have a lot of the attributes that people were looking for,” he said. “At $20 million, it’s a good buy. At $50 million, it was just ridiculous.”

Aspen, Colo.

In January 2021, Mr. Butterfield and Ms. Rubio paid $25 million for a mountain-style estate on 5 acres in the affluent Colorado community of Aspen. The house is their primary home, according to people familiar with the situation.

Located in the Five Trees neighborhood and with views over the Castle Creek Valley, the roughly 10,600-square-foot property, completed in 2013, has six bedrooms, a home theater, a gym, a bar and billiards area, a 500-bottle wine cellar and a tasting room, according to the listing. It also came with a three-car garage.

The interiors, designed by the New York studio of Sandra Nunnerley, included rustic beamed ceilings, floor-to-ceiling casement windows and wide use of Scandinavian woodwork. A rustic locker room is outfitted in Blue Spruce wood.

The deal was among the pricier transactions to close in Aspen in 2021 as the local market there rocketed to new heights amid the pandemic. It was deals such as this one that raised the bar for pricing in nontraditional areas, agents said.

Local agent Riley Warwick of Douglas Elliman, who wasn’t involved in the sale, called the property “a really good house,” but said it is located outside of what is typically considered Aspen’s most coveted neighborhoods. The Five Trees neighborhood logged a handful of deals over $20 million during the pandemic. “Before that, I think the highest sale there was around $8 million,” he said.

Recent Sales

Mr. Butterfield and Ms. Rubio have also sold some of their trophy homes in recent years.

They sold their San Francisco Victorian mansion for $19.155 million in October 2022. The seven-bedroom, nearly 8,000-square-foot house had bay windows and delicate Italianate details. They bought it for $19 million in 2019.

They also sold a Tribeca townhouse for $8.417 million in 2021, according to property records and a person familiar with the situation. The roughly 4,000-square-foot home is configured as a townhouse within a boutique condominium.