All taxpayer records appear on the Transcripts page. For business taxpayers, 1120 is available on the dropdown list for Record of Account transcripts, Tax Return transcripts, and Account Transcripts.
All versions of Form 1120 that the IRS has on file will appear in the same place (1120-S, 1120-C, 1120-F, 1120-H, 1120-L, 1120-POL).
If the field states "No record of return," the Account Transcripts can provide valuable additional information on the status of returns. This is where you would see if an extension has been filed or if the tax return has been received by the IRS but has not yet been processed.
Also see the FAQ for No Record of Return.