Six companies have submitted proposals for how to redevelop 20 acres on the west side of the Charleston peninsula. What those proposals are, the city won’t say.

Gary Cooper, the city’s director of procurement, released the list of companies Monday but said their exact ideas for the so-called Horizon Project will not be revealed during the review process.

The companies are:

Childress Klein Properties of Charlotte

Gateway Development of Atlanta

Azimuth Horizon Development Partners LLC of Greensboro, N.C.

Pizzuti Companies of Columbus, Ohio

Hughes Development Corp. of Greenville

The Furman Co. of Greenville

Horizon, a collaboration between the city, the Medical University of South Carolina and the South Carolina Research Authority, has been more than seven years in the making, in part stalled by the recession.

In September, Horizon officials announced the request for proposals — at the top of the Marriott hotel on Lockwood Boulevard overlooking the site bounded by Lockwood Boulevard, Hagood Avenue and Fishburne and Spring streets. Proposals were due at 4 p.m. Friday.

Now mostly open land or surface parking lots, the vision for Horizon is some 2 million square feet of apartments, offices and research space. The hope is for more than $1 billion in investment over the next couple of decades.

Similar grand-scale initiatives in other cities have bred controversy and had only limited success, but Mayor Joe Riley is aiming for a “nationally significant” makeover. Horizon is now in the midst of the next crucial step toward making the vision a reality.

“We’ll be very deliberate about picking a developer,” MUSC President Ray Greenberg said in September.

Reach Brendan Kearney at 937-5906 and follow him on Twitter at @kearney_brendan.