The Butterworth Building or Butterworth Block at 1921 First Avenue in Seattle, Washington (U.S. state) was originally built as the Butterworth & Sons mortuary, which moved into this location in 1903 and moved to larger quarters in 1923.  Located on a steep hill, the building has only three stories on the First Avenue side, but five on Post Alley. The building is listed on the National Register of Historic Places (NRHP); adjacent to Pike Place Market, it falls within the NRHP's Pike Place Public Market Historic District and the city's Place Market Historical District.

The building was the city's first purpose-built mortuary building. Jeannie Yandel in 2009 described it as "The city's first place for comprehensive death-related services from corpse retrieval to coffin sales."

Mercedes Yaeger, who runs Market Ghost Tours in Pike Place Market draws an analogy to a later Seattle business founded in the Market, and calls the 1903 mortuary "the Starbucks of the dead: in the same way Starbucks revolutionized the coffee business, E.R. Butterworth's mortuary revolutionized the death business." The building is associated with several ghost stories. The building had the first elevator on the West Coast of the United States, used to transport bodies.  A Seattle Mail and Herald account from August 1904, shortly after the building opened calls it "without question of doubt, the most complete establishment of its kind in the United States…" A 2008 Seattle Times article describes the building, still extant, as "[b]eautifully appointed in stained mahogany, art glass, ornamental plaster and specially designed brass and bronze hardware…" The basement, accessible through Post Alley at the rear, is now (as of 2009) home to Kells Irish Restaurant & Pub. Several recent accounts describe the Kells space as the former embalming room and crematorium, but the 1904 account says that the basement housed the building's heating plant, stables, and a storage space for funeral wagons.

The business was soon renamed E. R. Butterworth & Sons. Five of his sons joined him in the business: the aforementioned Gilbert Butterworth and his half-brothers Charles Norwood Butterworth, Frederick Ray Butterworth, Harry Edgar Butterworth, and Benjamin Kent Butterworth. Gilbert and Frederick would be the longest-lived, and were followed into the business by several of their own sons. By 1929, when Butterworth's son Gilbert was managing the business, it had already remained in the hands of a single family longer than any other Seattle funerary business. It would retain that status nearly until the family sold the business to New Orleans-based Stewart Enterprises in 1998, by which time it was one of the city's longest-running family-owned business of any type. The last Butterworth to run the business—which was by then Butterworth-Manning-Ashmore, after a series of mergers—was Edgar's great-great grandson, Bert Butterworth Jr.

From Second and Pike, the business moved to 1425 Second Avenue (later the 1896–1929 location of The Bon Marché department store); then to 1426-28 Third Avenue; and on October 1, 1903, to the custom built Butterworth Block at 1921 First Avenue. 1921 First Avenue now falls within the Pike Place Market Historic District, although the market was not founded until 1907. The building has been listed on the National Register of Historic Places since May 14, 1971.

The Butterworth Block or Butterworth Building was the city's first custom-built modern mortuary.  Jeannie Yandel in 2009 described it as "The city's first place for comprehensive death-related services from corpse retrieval to coffin sales." The building had the first elevator on the West Coast of the United States, used to transport bodies. A 2008 Seattle Times article describes the building, still extant, as "[b]eautifully appointed in stained mahogany, art glass, ornamental plaster and specially designed brass and bronze hardware…" The basement, accessible through Post Alley at the rear, is now (as of 2009) home to Kells Irish Restaurant & Pub.

In 1923, the business moved again, to a building on the northeast corner of Melrose Avenue and Pine Street, also extant as of 2009. Clarence Bagley, writing in 1929, described the building as having a crematory and columbarium, fireproof receiving vaults, a funeral church and chapel, and drawing rooms, and utilizing "Cadillac motor equipment with special designed bodies" as their hearses, stocking "funeral furnishings… from the most simple to the magnificent." The former chapel of the Melrose mortuary now houses the bar Chapel. Whereas few traces 1921 First Avenue's original use remain at Kells, Chapel retains "leaded glass windows and enormous mirrors, ornate dark woodwork, vaulted ceiling, antique fixtures" and the white stone material composing the bar was also salvaged from the prior use.

Although the family is no longer in the business, the name lives on in the Butterworth-Arthur Wright Chapel at Mt. Pleasant Cemetery on Queen Anne Hill.

On All Saints Day in 2005, Karen McAleese says she saw something she still cannot explain walk through the kitchen of Kells pub, which her brother owns.

'He was a tall man who looked like he was part black, with a suit jacket on,' she reported to the Seattle Times.

'He had very thin hands. He walked to the end of the bar and just kind of faded.'

McAleese believes that spirit, along with others supposedly spotted in the building over the years, belongs to one of the thousands -- perhaps millions -- of dead people who passed through Kells back when it was E.R. Butterworth and Sons Mortuary.