  The relationship between nature contact and mental well-being has received
increasing attention in recent years. While a body of evidence has accumulated
demonstrating a positive relationship between time in nature and mental
well-being, there have been few studies comparing this relationship in
different locations over long periods of time. In this study, we estimate a
happiness benefit, the difference in expressed happiness between in- and
out-of-park tweets, for the 25 largest cities in the US by population. People
write happier words during park visits when compared with non-park user tweets
collected around the same time. While the words people write are happier in
parks on average and in most cities, we find considerable variation across
cities. Tweets are happier in parks at all times of the day, week, and year,
not just during the weekend or summer vacation. Across all cities, we find that
the happiness benefit is highest in parks larger than 100 acres. Overall, our
study suggests the happiness benefit associated with park visitation is on par
with US holidays such as Thanksgiving and New Year's Day.
