As the summer months drag on, the high temperatures make us nostalgic for summers gone by. Not all summer memories, though, recall beaches, bungalows and ice cream parlors. 

Urban summers have their own share of charm and magic: A businessman wiping his brow as he walks determinedly down Fifth Avenue, a little girl as she finds a penny in the sidewalk’s tessellated crack, a young couple as they fan each other on the subway platform. 

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The subway system is a large part of urban summers. A staple in populous urban cities, the Underground was first developed in London in the late 19th century. When "rapid transit" started spreading in 1896, it spread quickly -- first to Budapest, then Paris, then Boston. Next came New York in 1904, Philadelphia in 1907 and Moscow by the 1930s.

Click through the slideshow above to get a look back in time at the “straphangers” of old, who battled heat, bus strikes, wartime uncertainty and more.