The two Saharan countries have been at odds since 1975, when Spain pulled out of Spanish Sahara (now Western Sahara). Morocco, in what was seen as a simple land-grab by many in the region, marched south, annexed Spanish Sahara and successfully quashed any attempt at self-rule. Algeria has been a foe of Morocco ever since. When diplomatic relations between the two completely collapsed, they closed their border in 1994. Now, one side seems to be softening its position, perhaps for economic reasons (is Morocco needing oil?).
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Map Morocco willing to normalise bilateral relations with neighbouring Algeria - 20 April 2009
[...]
After 15 years of political rivalry, the Moroccan authorities have expressed their eagerness to normalise ties with Algiers. The border between the two countries [has been] closed since 1994.
According to Yahoo, Moroccan Foreign Minister Taieb Fassi Fihri said on sunday that '[...] it would be a "win-win situation" if the conflict was resolved by the United Nations so that bilateral relations could resume.
The Algerian-backed Polisario independence movement has disputed Morocco's claim to Western Sahara since Rabat annexed it in 1975 after former colonial power Spain withdrew.
UN chief Ban Ki-moon said in a report on Tuesday that Morocco and the Polisario remain far apart on how to settle the Western Sahara dispute, and that a resumption of stalled talks needs careful preparation.
Four fruitless rounds of UN-brokered talks in the New York suburb of Manhasset since 2007 have failed to resolve the long-standing dispute.[...]
Source * Edit: I've found several recent articles about the border issue that confirm the economic agenda for this potential change. Several north African countries have been working at forming an economic union similar to the EU, which could raise the standard of living in all of them.
Algeria, Morocco working on closed border issue, Algerian minister says 2009-05-11
The governments in Algeria and Morocco are working together to settle the closed border issue, for the benefit of the businessmen in the region, Echorouk quoted Algerian Industry Minister Abdelhamid Temmar as saying at a press conference on the sidelines of the
Maghreb business forum Sunday (May 10th) in Algiers. "Closed borders must be opened to allow Maghrebin businessmen to benefit from advantages in all the countries," Temmar said.
This content was commissioned for Magharebia.com. Source This border crossing does indeed look unused. (An interesting note: as you travel north to the city of Figuig, Morocco, you will see a
qanat, an ancient type of irrigation system. It's the long row of holes on the right of the highway. Our old friend danescombe educated me about
qanats.)