You could see this one coming a mile away: Social image-sharing site Pinterest has finally cracked comScore’s monthly list of the top 50 web properties in the U.S.

The September Top 50 is just out, and Pinterest squeaked in at No. 50 with an estimated 25.3 million visitors.

That puts it still slightly behind the declining MySpace (26 million estimated visitors). Instagram and Tumblr are also slightly ahead and Pinterest and stand at 44th and 42nd, respectively.

Pinterest has been growing dramatically for at least a year, but its recent growth is no doubt being fueled by the site’s decision in August to open registration to anyone, no invitation required.

The Pew Research Center’s Internet & American Life Project recently estimated that 12 percent of all internet users use Pinterest — including 19 percent of all female internet users. The company’s recent mobile app upgrades should continue to drive adoption and usage.

The top five sites overall on comScore’s September list are unchanged from August. One notable decline involves the Ask Network, which was No. 7 in August with an estimated 89.4 million visitors. For September, it’s dropped to 12th with an estimated 78 million visitors.

Related Topics: Channel: Strategy | Pinterest | Pinterest: Statistics | Social Media Marketing | Statistics: Popularity & Usage | Statistics: Social Media | Top News

About The Author: Matt McGee is Editor-In-Chief of Marketing Land. His news career includes time spent in TV, radio, and print journalism. His web career continues to include a small number of SEO and social media consulting clients, as well as regular speaking engagements at marketing events around the US. He blogs at Small Business Search Marketing and can be found on Twitter at @MattMcGee and/or on Google Plus. You can read Matt's disclosures on his personal blog. See more articles by Matt McGee

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