At the same time, to me his paintings are almost all about the inevitability of loneliness. All his images of cities and city streets seem to make the city beautiful but oppressive. The public spaces -- streets, cafes, big urban windows -- just seem all the more distant. Looking through his eyes at other people talking intimately always gives me that feeling of being a stranger, of walking through a city where you don't know anyone or anything, of 'not speaking the language'.
In this light, instead of being comforting, Hopper's virtuosic use of light becomes something frightening, alien, and harsh. Here light is something to shy away from. Yikes! Kind of a terrible vision of the city, but one that still enchants me.
"Hopper became a pictorial poet who recorded the starkness and vastness of America. Sometimes he expressed aspects of this in traditional guise, as, for example, in his pictures of lighthouses and harsh New England landscapes; sometimes New York was his context, with eloquent cityscapes, often showing deserted streets at night. Some paintings, such as his celebrated image of a gas-station, Gas (1940), even have elements which anticipate Pop Art. Hopper once said: 'To me the most important thing is the sense of going on. You know how beautiful things are when you're travelling.'
"He painted hotels, motels, trains and highways, and also liked to paint the public and semi-public places where people gathered: restaurants, theatres, cinemas and offices. But even in these paintings he stressed the theme of loneliness - his theatres are often semideserted, with a few patrons waiting for the curtain to go up or the performers isolated in the fierce light of the stage.
[Mark Harden's Artchive]
Urban architecture and cityscapes were also major subjects for Hopper. He was fascinated with the American urban scene, “our native architecture with its hideous beauty, its fantastic roofs, pseudo-gothic, French Mansard, Colonial, mongrel or what not, with eye-searing color or delicate harmonies of faded paint, shouldering one another along interminable streets that taper off into swamps or dump heaps.” 
In 1925, he produced House by the Railroad. This classic urban work depicts an isolated Victorian mansion and marked Hopper’s artistic maturity. Critic Lloyd Goodrich praised the work as “one of the most poignant and desolating pieces of realism.” The work is the first of a series of stark urban and rural scenes that uses sharp lines and large shapes, played upon by unusual lighting to capture the lonely mood of his subjects.