This postcard is postmarked 1923 and is labeled West Water Street. Around a decade after this postcard was sent, Milwaukee would rename the street as North Plankinton Avenue, which is how we know it today.
This view is facing south toward Wisconsin Avenue (which, as of the postmark date, would have been named Grand Avenue). In the center is the Gimbels Building. Adam Gimbel first opened a shop in Vincennes, Indiana in 1842. He and his seven sons (the Gimbel Brothers) eventually relocated to Milwaukee in 1887, renting space from John Plankinton on the corner you see here. The retail operation rapidly expanded into adjoining buildings, and in 1902, Gimbel demolished the original three-story building on the southeast corner of Water and Grand (now Plankinton and Wisconsin) and built the eight-story structure you see in this postcard. This Gimbel building, designed by D.H. Burnham and Co. of Chicago, was the first of many adjoining structures that the Gimbel Brothers would build in the following decades to expand into the entire block along the river from Wisconsin Avenue to Michigan Avenue.
On the near corner on the left, across Wisconsin Avenue from Gimbels, the Empire Building (containing the Riverside Theater) would be built five years after this postcard was sent. The much smaller building you can see in this postcard on the corner was also known as the Empire Building, and it was built around 1898. This building featured the Empire Café on the corner of the ground floor. It was also known as the Browning Building from 1921 until 1927, when it was razed to make way for the current Empire Building and Riverside Theater.
The white building on the far left is now the Riverfront Lofts. Built in 1916, the building was a furniture store and warehouse for Waldheims and Nelson Brothers over the years.
Sources:
https://www.wisconsinhistory.org/Records/Property/HI16193
https://www.wisconsinhistory.org/Records/Property/HI41778
https://www.wisconsinhistory.org/Records/Image/IM47664
Milwaukee Journal Sentinel, June 19, 1997: https://0-infoweb-newsbank-com.countycat.mcfls.org/apps/news/openurl?ctx_ver=z39.88-2004&rft_id=info%3Asid/infoweb.newsbank.com&svc_dat=WORLDNEWS&req_dat=0D8DE8DE83992E4A&rft_val_format=info%3Aofi/fmt%3Akev%3Amtx%3Actx&rft_dat=document_id%3Anews%252F0EB82ABB00487972
Identifiers:
PLUS code: 23QQ+Q7 Milwaukee, Wisconsin
Approximate Google Street View today: https://goo.gl/maps/HSCZKTDiGqwZekFm8