I was wondering about this the other day, and I couldn't recollect any specific point where the trend appears. Was it an old custom that evolved over time, or was it something in response to the housing boom post-WW2? I may be wildly off, but I would love to hear some insight.
Here is a previous thread addressing that question, including citations. Apparently mowed or trimmed lawns began on English estates and parks due to the climate, became more popular among the middle-class in the late 19th century when maintenance had become less expensive and the middle-class had grown more affluent, and became popular in American suburbs in the mid-twentieth century when affluence and suburban sprawl made it very affordable.
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