BANGKOK - For people who have stood at a monument or scanned a landscape -- the Great Wall of China, for instance, or the US Grand Canyon -- and wondered how it looked 100 or more years ago, there is now an app for you.

Historypin, on iOS and Android platforms, strives to create a collection of memories about locations by counting on people to dig up and digitize old photographs and other media of the places, along with personal recollections of the past.

Combined with modern pictures and memories, the app creates a story of a place for people to enjoy -- a sort of "time machine in your pocket," its backers say.

"It's about people coming together to create a web of human history", said Nick Stanhope, chief executive of We Are What We Do, a United Kingdom-based non-profit organization responsible for the Historypin project.

The app uses GPS to find content that has been added within a certain vicinity. Users can also browse content that has been uploaded at any location on the map. The results can be filtered by date, ranging from the 1840s (the time of the earliest photographs) leading up to the present day.

The app also includes an augmented-reality camera that overlays historic images in the database on top of the current landscape. Over 55,000 photos and stories have been pinned to the map since the website and app were introduced.

One photo from 1938 shows a car being tugged across Newfoundland, Canada's Placentia Gut by two small wooden boats, a method that was retired as soon as a bridge was built to provide a more efficient route.

Another from the late 1920s shows a mother and daughter in Minnesota enjoying a laugh in front of a local school and its now defunct bell and tower.

Users can create or upload content using the app. Comments can be added to existing media, helping build what the organization hopes will become a tapestry of historic data.

"We don't make any judgments on what is and isn't history", said Stanhope. "But there are judgments made on things like marketing spam or unrecognizable content."

With the ubiquity of digital content today, some users are concerned that Historypin could become a dumping ground for social photos that might be a better fit for a Facebook album.

"Obviously a guy falling out of a bar in Manhattan in September 2011 is not interesting in itself", said Stanhope.

"But when you look at what people have done at that location over the past 200 years, it becomes interesting -- and over time it becomes more interesting. If you look at people socializing or having a party 100 years ago, suddenly it's fascinating."

The app, which has received over 250,000 downloads, has faced some speed and stability complaints since launching. Stanhope said the organization is providing upgrades every few weeks to address the issues.

New tools being rolled out in January are expected to significantly increase the amount of content in the database, as are partnerships in the works with US museums.

Stanhope said that future updates will include features to increase the accuracy and amount of detail attributed to content and the introduction of a rating system.

The app is available worldwide on the App store (http://itunes.apple.com/us/app/historypin/id455228207?mt=8)  and Android Marketplace (https://market.android.com/details?id=com.historypin.Historypin).  Content can also be explored through the project's website.