When incorporating our business, what happens to the software intellectual property we previously created as a team?

We have been working on a new software product as team of four, located in MA, USA. As a team of engineers, we never really talked about the Intellectual Property included in our product. However, we would like to make a step towards bringing the product to the market, incorporating as a company. What happens to the IP we created together and how do we know who owns what?