1) Eastmans' MRS sections are the most easily accessible trophy information and they do a great job on identifying trophy potential for various hunt codes and often counties. Plus, it is always up to date.
2) Spend $50 and buy the Boone & Crockett Records of North American Big Game Each listing gives the location of the trophy http://www.boone-crockett.org/store/...&action=detail
3) Spend $100 to join Safari Club Intl (SCI) and get the ability to search their record book by location for a year. A membership in B&C will also let you search their database.http://www.scirecordbook.org/index.cfm
4) Call CO FWP at (303) 297-1192 and ask if they still keep big game size records. They do for fish but the the last published edition I know of for big game was in 1983.
5) Look at this list from B&C of the 125 U.S. counties with the most listings overall for big game, not individual species. Within each species they will list the top counties in that list by how many entries for that species they had but they will not list every county's numbers for every species. That is NOT the same as which are the best B&C counties for a specific animal like say elk. That's probably clear as mud, but look at the list and you'll see what I mean. http://www.boone-crockett.org/news/f...ea=news&ID=154
What you will find in that list is that the number of CO counties in B&C's top 125 list overall that have the most listings for elk is zero. Instead, the counties in the top 125 overall that are remarkable for elk are all in AZ, NM, WY, and NV.
However, several CO counties are listed because of their numerous record listings for mule deer. That tells me that if those counties hold elk, and nearly all do, they apparently have the minerals in the soil to produce big antler growth. So, that may be a decent proxy. Here are the counties:
29. Colorado, Eagle County--67 typical mule deer in B&C records
45. Colorado, Mesa County--47 typical mule deer in B&C records
54. Colorado, Garfield County--44 typical mule deer in B&C records
67. Colorado, Gunnison County--38 typical mule deer in B&C records
75. Colorado, Montrose County--35 typical mule deer in B&C records
77. Colorado, Delta County--34 typical mule deer in B&C records
84. Colorado, Montezuma County--33 typical mule deer in B&C records