The two largest organizations in genealogy are embarking on a resource-exchanging partnership that will put more records online—starting with US censuses.

Under the agreement, enhanced census indexes will be free for a limited time on Ancestry.com and permanently on FamilySearch. Record images will be available by subscription on Ancestry.com and free at FamilySearch’s 4,500 worldwide Family History Centers, as well as National Archives and Records Administration (NARA) regional facilities.

FamilySearch, which is digitizing census records at NARA, will provide its record images to Ancestry.com. These newer images, created with more-recent technology, are of better quality than those available on Ancestry.com.

Ancestry.com will give FamilySearch its indexes to censuses from 1790 to 1930. FamilySearch Indexing volunteers will use them as a “first draft,” double-checking information and adding data fields (such as birth month and year) to create an improved index.

FamilySearch volunteers already were indexing some censuses, following a two-pass, arbitrated system: Each record is indexed twice by different people; a knowledgeable third person resolves any differences in the versions. The volunteers have completed a 1900 census index, now free at FamilySearch Record Search.

These existing FamilySearch indexes will be merged with Ancestry.com’s indexes. (If a person’s name is indexed under different spellings, both spellings will remain.)

The partnership’s first exchange is the 1900 census. The improved record images are on Ancestry.com now; the merged index will become available in August. Other censuses will be released over the next several years as the images and indexes are completed.

The census indexes on Ancestry.com and FamilySearch will link to record images on Ancestry.com. If someone without an Ancestry.com subscription clicks the image link, he’ll be prompted to join. Subscriptions cost $155.40 per year or $19.95 for a month.

Ancestry.com has long been the target of complaints about its census indexes, so the company and its subscribers will undoubtedly welcome the new-and-improved versions.

Friday, I had a chance to talk with representatives of both organizations, who agreed genealogists will appreciate the broader access to records, improved indexes and higher-quality digital images. On some record images, you even can see previously indiscernible notations, according to Ancestry.com vice president of content Gary Gibb.