Why were the Articles of Confederation our first form of government; why did they use this model?

We were in the middle of the Revolutionary War, 13 separate colonies. There was a fear that the Brits would win back a few, the easy ones, and leave the rest. The revolutionaries realized we needed some kind of document that tied all the colonies together, so the 13 colonies as a whole could either win or lose.

So delegates got together from all 13 colonies and tried to hammer out a document they could all agree with. They found (to nobody's surprise) that they couldn't agree on a lot of things. These issues would take time to discuss, negotiate, and come to an agreement on, but there wasn't time to do that.

So they decided the document would just be a framework, just the simplest agreement possible. Rather than a federal system like we have today, it was really just a 'league of states', each state individually sovereign. Every state had its own currency, its own laws, etc. The govt. of the nation was very small and weak and really had no power over the states. That was all that was needed at the time.

But there were serious problems with it. For instance, each state had its own currency so if you wanted to do business in all 13 states you had to keep track of exchange rates. Each state had its own roads so if you wanted to go through one state to do business in the other, that state could charge you a toll to travel through it. The fed. govt. was sort of like the UN today. It provided a forum but didn't have the power to tell member states what to do.

After the war was won, the delegates came back together in Philadelphia to come up with a better document, one that divided power between states and the federal government, and gave the federal govt. power to coin money, regulate interstate commerce and foreign policy, etc. To their great credit (IMO) they managed to resolve all their differences through compromise! That was the Constitution, and we still have it today, with surprisingly few changes in 230 years.

It was used temporary to conclude the American War of Independence against Great Britain. The War ended in real terms 1783. 4 years later in 1787 the great Constitutional Convention was called to make a real and permanent government.
The 'Articles' were in effect for only 4-7 years as they were always temporary.