If you want to know the background, or history, of a section of the CFR, there are a few steps you can take.
STEP 1 - Look up the most current version of the CFR section. 
Note: When using the lookup, be careful when using the Restrict by Year options - remember that the CFR rolls out throughout the year, so titles with higher numbers show up later in the year. As an alternative, simply don't use the pull down and all version will show up with the most recent year published at the top.
STEP 2 - From your search results, select (click to open) the most recent CFR version.
STEP 3 - Scroll to the section of the CFR you are studying. Note that at the bottom of the part, a history of that section with Federal Register (FR) citations will be listed. Note also that on the left, you can view the PDF version of the section.
Note: You will want to copy that history into a document or email so that you can keep track of your work.
Tip: If you are searching within a large section of the CFR, search for FR [or allcaps(FR)] within the document to find the citations to the section history.
STEP 4 - To research the history, you will now want to search on each Federal Register citation to find the language for the proposed rules.
In this case, there are four different rules that were published in the Federal Register: 53 FR 4525, 59 FR 61501, 71 FR 76944, and 74 FR 19005. It can be easier to search each of these individually, then use the information you find to look for the proposed rule language.
Older rules may not include a RIN number or a Docket Number. See 4A, below, for how to located the proposed rule language.
Newer rules should include a RIN number or a Docket Number. See 4B, below, to efficiently use that information to find the proposed rule language.
STEP 4A - When you search for the rule, if the header information does not contain a RIN or Docket number, you will need to read the Federal Register notice to find the citation to the proposed rule.
For example, this oldest citation 53 FR 4525 does not contain a docket number or RIN in the details listed.
Here is the Federal Register article showing the citation for the proposed rule language.
You may want to take advantage of some of the advanced search functionality in Adobe for more precise searching. See our guide here.
STEP 4B - When you search for the rule, if the header information does contain a RIN or Docket number, you can use the information from your rule search to find the citation to the proposed rule.
For this example from 2006, the details show both a Docket and a RIN listed.
Go to the Search by Number search form and scroll to the bottom to use those numbers to find proposed rule language.
If your RIN or Docket number search does not produce results, you'll need to use the strategy in 4A (above) to ensure you have all the information.