If it's a genuine San Francisco police thriller then it has to include the old Hall Of Justice. This movie is no exception.
Then ... Taking a break from the murder investigation the two brothers leave the Hall Of Justice, stepping out to Kearny Street for a Chinese lunch.
The same shot was used a year earlier in the 1949 movie Impact.
... and Now, the old Hall Of Justice faced Portsmouth Square Plaza from its location at 750 Kearny Street in Chinatown. It was demolished in 1967 and replaced by a Holiday Inn hotel, now the Hilton San Francisco Financial District (map).
Then ... They walk the few steps to the Yen Yen Cafe at 716 Kearny on the corner of Merchant Street. Its sign juts out, just above Andy's fedora.
Three years earlier in the 1947 movie The Lady From Shanghai, the identical camera placement captured Orson Welles fleeing from the Hall of Justice with the Yen Yen Cafe sign again clearly visible.
... and Now, there's still a Chinese eatery, the Garden Restaurant, at that corner location. But at left we see that the imposing Hall Of Justice is gone.
Then ... Inside the cafe Andy cannot understand why Ed persists in trying to pin the Frazer murder on the youth who shot the liquor store owner. Yes it was the same gun but the evidence suggested he didn't have access to it until after Frazer was killed. Portsmouth Square Plaza is seen across Kearny through the window but what's that white building in the park?
... and Now, the plaza today is no longer a gently sloping open space - it was sacrificed to make way, behind these trees, for an uninspiring two level park with underground parking.
And that white building? It was a replica of the city's first schoolhouse, originally located at Portsmouth Square, which happened to be on display in the plaza for the California Centennial observance when the movie was filmed. Here's the schoolhouse in 1951 as it was being moved from the plaza to City College, slated to be a museum exhibit.
There isn't a view of the front of the Yen Yen Cafe in the movie but in this capture from The Lady of Shanghai filmed three years earlier as Rita Hayworth runs through the plaza we can see the half block of Kearny between Merchant (just off the left edge of the picture) and Clay Street to the right. The white van on the left is parked in front of the cafe. The awning just to the right of the van belonged to Puccinelli Bail Bonds at 714 Kearny (also visible in the other Lady From Shanghai image above).
... and Now, the half block today still looks the same except for different store tenants. The Garden Restaurant at left has expanded from the original Yen Yen Cafe corner space and now spans the full width of the host Wood Building.
  After she discovers the two bodies Helen decides she doesn't want to get involved - she was just about to leave Reno for home anyway so she heads straight to the station for the late night train to San Francisco.
... from 1928 ... The Reno depot was built in 1925 by Southern Pacific. This postcard image shows the station three years after it went into service and it still looked like this in 1947 when the movie was filmed. The station fronts E. Commercial Row but this view, from Lake Street, of the rear track-facing side of the building shows us where the following scene was filmed (map).
... and Now, because the depot is in the center of town the tracks have since been lowered and street-level bridges built to alleviate traffic-crossing problems. The depot has been kept in its original form and the building is now on the National Register For Historic Places.
Then ... While Helen waits for the train (her luggage is on the left) who should walk up but Sam (the killer - we know it but she doesn't, yet). He too is making a hasty exit from the scene of the crime.
... and Now, the red border outlines the same part of the depot (CitySleuth must confess that he used the front exterior for these comparisons because 1) the rear is harder to photograph the matching shot due to the major changes resulting from lowering the track, and 2) the depot architecture is identical front and back.
Then ... They strike up a conversation, recalling their first meeting in the casino. Sam offers to carry her luggage onto the waiting train and she is quite happy to accept.
... and Now, the red border outlines the same part of the depot (again using the more accessible but identical front of the building).
... and Now, this recent photo taken track-side shows where the filming took place, on the right, before the tracks were lowered.
 In the club car they waste no time flirting with each other as the train pulls out past the glitter of downtown Reno.
Then ... By the time they get on the ferry at Oakland Pier to complete the journey to San Francisco it's obvious they will continue to see each other. But wait a minute ... there's a continuity goof in this footage - with Yerba Buena Island on the left this is a view from San Francisco showing the ferry going in the wrong direction, cruising under the Bay Bridge from left to right towards Oakland.
Then ... But in the next shot their ferry is on the other side of the bridge and heading, correctly, towards San Francisco.
... and Now, six decades of development has transformed the San Francisco shoreline.
( A Bunker Hill movie in a San Francisco blog? CitySleuth explains why).
How does a filmmaker keep the viewer entertained during a voiceover? Director Kent MacKenzie used several voiceovers in this movie and his solution was to fill in the time with downtown street scenes filmed at night using the street lamps, retail shop window lights and neon signs as highlights. They were all located within a few short blocks.
Then ... In this shot we can see the tower of City Hall in the upper right corner.
... and Now, the view looks north along Main Street with 3rd Street crossing in the foreground (map). City Hall is still there but the corner building at left has had the upper two stories removed. What is unusual is that its retail stores were left in place - the previous location showed surviving threshold tiles in one of the stores in this block.
Then ... Here's a bustling street corner.
... and Now, this is at the same junction as the prior scene, Main at 3rd. The store on the left, on the northwest corner, is now the Persian restaurant Shish Kebob but back then was called Optimo (you can see it in the first 'Then' image above). El Progreso across the street was at 260 S. Main Street but this half of that block is now a parking structure.
Then ... This was filmed from below the Angels Flight funicular as one of its cars approached the lower terminus at Hill and 3rd (map). As we look east from here along 3rd Street the F P Fay Building sign is seen at right across 3rd and that hotel facing us a few blocks down is the St. George at 115 E. 3rd Street. Hard to see from here but below the word 'HOTEL' is a stylized 'One Dollar' sign, its daily room rate.
... and Now, the funicular has been moved a half block south along Hill Street and the old F P Fay corner building on the right has been replaced by a parking structure. The St George hotel, distantly small in this non-telescopic photo, is still there, now providing low income housing.
... in 1952 ... the St George survived a fire a few years before The Exiles was filmed, captured in the photo below which clearly shows the stylized 'One Dollar' neon signs (the one on the left is the one visible in the 'Then' image above). Incidentally the Enderle hardware store, on the left below, and a recent photo of the St. George can be seen here in an earlier post.
Then ... More drinking joints but this shot includes an architecturally interesting building on the left. This is the south side of the 300 block of 3rd Street (map). From left to right were Radio-Electronics at 316 S Main, a liquor store and Saddle Rock Cafe at 320, the posh entrance to the F P Fay Building at 326, and Buggy Wheel Cafe at 328 (most bars in those days seemed to prefer the pseudonym 'cafe'. Who were they kidding?).
... and Now, the stylish building with the arches, an extension of the Metropolitan Water Board Building, is still there but those on the right including the F P Fay building have been replaced by a parking structure.
Then ... The shooting suspect flees from the rear of the 322 Club (see previous location) closely chased by detectives Ed and Andy Cullen. By way of the power pole he climbs to a fire escape ladder leading to the roof.
... and Now, this is in Wentworth Place in Chinatown, looking south to Washington (map), looking much the same other than newer lampposts and newer buildings towering in the distance.
Then ... Viewed in the opposite direction, Ed Cullen and some passers-by watch as Andy pursues the suspect.
... and Now, with Jackson Street crossing at the end of the narrow street it's hard to know if this is 1950 or 2013. Don't you just love Chinatown!
Then ... But as Andy reaches the roof we are back in Telegraph Hill! Note the semi-circular tiled bay window roof on the house across the street ...
... and Now, here's that same house, it's at 330 - 334 Union Street. The Russian Hill skyline is in the distance.
... and Now, across the street the arrow shows the ladder that Andy used, above - it's the fire escape of the corner building complex that housed the old Speedy's Grocery store, now Acre/SF (map). The doorway next to the store was the entrance to the 322 Club as described in the previous location. Montgomery Street is on the left.
Then ... The rooftop chase reveals some cross-city views, this one towards Nob Hill. On the skyline we see, from left to right, the Brocklebank Apartments (used as Madeleine's home in Vertigo), the partially built Grace Cathedral - then with only one tower, the 1250 Jones Street Apartments dead center and the Bently Nob Hill Apartments at 1360 Jones.
... and Now, there are many more buildings dotting the skyline these days but those mentioned above are still there. The completed Grace Cathedral has twin towers; from the vantage point below they are hidden by the dark grey newer building but we can see its spire, yet to be built in the view above. Today 1250 Jones is even more recognizable by its radio mast.
Then ... The suspect desperately looks for a way down ... the view past him follows Montgomery Street to the south. The white building partially visible on the left is the Appraisers building at 630 Sansome Street. Note that tiled hexagonal roof (arrowed) ...
... and Now, believe it or not, this is the same view down Montgomery - more than any other part of town the financial district has became the most changed.
... and Now, the tiled roof arrowed in the Then image above is at 1235 Montgomery (left arrow, below) and the suspect was on the roof of number 1255 (right arrow). 1255 has been remodeled or rebuilt since then; its original roof was lower. The contemporary white building in the center wasn't there in 1950; it was a vacant lot.
Then ... It's supposedly the same roof but this shot cuts to a different location, obviously chosen because of three convenient level changes down to the street allowing for an easy (for the agile that is) descent.
... and Now, he was on the rooftop of 23 - 25 Castle Street, a narrow alley between Union and Green just a half block from where the preceding rooftop shot was filmed (map). This nicely framed view from Green is enhanced by the nearby Coit Tower.
The pursuing Andy looks on as his brother Ed nabs the suspect right after he climbs down. They've caught the liquor store killer but Ed's lame attempt to blame his lover's husband's murder on him (remember, it was the same gun) doesn't fit the known facts.