The Cambridge Historical Commission shows us what the new Longfellow Bridge looked like in 1908 - a couple years after it opened - as the Cambridge Bridge. Look at those gasometers in Kendall Square on the Cambridge side.
The Boston Public Library has some Longfellow Bridge photos from back in the day as well:
Hey, where'd Storrow Drive go? Oh, yeah, when Francis Getty painted this scene in 1931 or so, it didn't exist.
This 1925 Fairchild Aerial Surveys photo from above Kendall Square shows Boston in the depths of a slow, decades-long decline, when downtown had just a single skyscraper:
A closer look at the Cambridge side of the bridge in 1932:
These days, directors tend to use the Zakim or even the Tobin as shots to establish the movie or show you're about to see was filmed in Boston, but once, the Longfellow was THE bridge to shout "Boston" - as in the opening of Spenser for Hire:
BPL images used under this Creative Common license.