This collector's guide focuses on the history of modern bar-and-pin style buckles for belts. On this page, I'll provide a brief overview of the invention of buckles and their evolution leading up to modern buckles that gained popularity in the 1960s. This guide also has a short section on civil war buckles; however, this is not my area of expertise. There is a passionate community of civil war collectors and history buffs who are far more knowledgeable on 19th century buckles than I am. Belt buckles from the 1970s and onward are my area of interest and expertise. Click the button below to access my other articles on modern belt buckle history.
BELT BUCKLE ORIGINS
The word "buckle" applies to a broad family of hardware used for fastening cords or straps. The history of buckles traces back at least 2,000 years to the age of the Romans where they were developed for military applications to hold straps for sword scabbards and horse-riding gear. The technology has remained unchanged for millennia. Today, buckles are used for equestrian riding gear, shoes and other apparel, for securing cargo (ie ratchet straps), safety devices such as seatbelt buckles, and other industrial applications.
Chris Marshall, a metal detectorist, created a website in 2002 with a photographic catalog to document the evolution of buckles throughout the Anglo-Saxon and Medieval periods. It is based on a combination of his own discoveries and research as well as a series of articles published in Treasure Hunting magazine in 1986. Marshall’s website is by far the most comprehensive narrative that I have seen on early buckles.
If you are interested in the early history of buckles, I encourage you to dig through Marshall’s articles.
His work has been captured by the Internet Archive, a nonprofit organization dedicated to preserving old web pages, and can be accessed here: https://web.archive.org/web/20101125185324/http://netmarshall.co.uk/buckletitlepage.htm
Here is a block quotation from Part One of Marshall’s writing:
The Oxford dictionary defines the buckle as a metal rim with hinged, spiked tongue for securing a strap or ribbon etc., and the name is derived from the Latin buccula (cheek-strap or visor). Here we have a clue to the possible origin of the buckle as a piece of cavalry or military equipment amongst the Romans, and it is true that there is no evidence of the use of buckles in England before the Roman invasion. It is likely therefore that the buckle was introduced by the Roman army and subsequently copied and produced by the native bronzesmiths (see fig.1 no 31). The history of the buckle is allied closely to the development of costume and the loose and flowing garments of the civilian Roman at this time did not require the use of buckles. This is clearly demonstrated when comparing the number of brooches and dress pins found on civil sites with the number of buckles.
The Roman soldier certainly did use buckles on his swordbelt, baldrick, and also for strapping together his laminated plate armour, and this is attested by the numbers that are found on fortified sites. Roman villas have produced a few examples of military type buckles - particularly of the 4th-5th century AD and this has led some people to conjecture that these sites may have been defended at some stage against Saxon raiding parties. By far the greatest number of these buckles however, particularly in the earlier period, has been found in Roman military contexts.
Whenever a strap or belt was employed the buckle was by far the best way of providing a secure attachment and a ready means of adjustment. No doubt at an early stage the buckle would also have been adapted for use on military horse harness. 
CIVIL WAR UNIFORM BELT PLATES
In the American Civil War, soldiers often wore metal belt buckle “plates” that were larger than early buckle designs and more closely resembled modern day bar-and-pin buckles. The front of the buckle plate was typically adorned with artwork or abbreviations to denote the soldier’s army division or state of origin. Over the years, civil war belt plates became—and have remained—hugely popular with collectors. Buckles from the Southern Army are rarer, and therefore more valuable, fetching prices of up to $35,000 for some rare designs. Even the most common civil war belt buckles, (photographed below) can be worth $300.
The strong collector’s market for these buckles has provided an opportunity for modern counterfeits to begin circulating into private collections. In addition, civil war reenactors wanted authentic looking buckles to include in their uniforms, so several foundries arose to meet the market demand and create precise reproduction buckles. Over time, the variety of authentic civil war buckles, legitimate reproductions, and reproductions sold as originals have created confusion in the marketplace and it takes a well-trained eye to discern which are authentic. The online offerings from amateur sellers on platforms such as Ebay often have bad or misleading information. I suspect these efforts are not malicious, there is simply a lack of information about the origin of many early belt buckles.
This segment from PBS’ Antiques Roadshow provides a great overview of the collector’s market for civil war-era belt buckles. 
For more information on reproduction buckles and fakes read through my 1970s History section.
EARLY 1900S SLIDE BUCKLES
In the early 1900s, slide belt buckles found popularity among businessmen and professionals. Slide or compression buckles used a latch to fold over the belt and hold it in place with a friction fit. One of the best-known buckle makers was Hickock, founded in 1909. They produced a variety of men’s belt buckles that were smaller and sleeker than military-style belt plates. The buckles often featured a monogram pattern with letters or personalized initials, polished to a high shine. Hickock was especially active from the 1920s through the early 50s, and by 1949 the company had $20 million in annual sales and 2,500 employees . The buckles were frequently sold through mail order magazine and newspaper advertisements, a business model which persisted into the 1960s and 1970s.
Sterling silver slide buckles were also manufactured in Siam (now Thailand) and Japan in the 1940s. The buckles may also be marked “Niello”, the name for the artistic technique using black inlay made from copper, silver, and lead. The inlay was carved away by hand to produce a high contrast engraving where the polished silver shone against the black background. (See example in photograph below) Nielloware jewelry was a popular as souvenirs for Americans fighting overseas during WWII and many nielloware slide belt buckles eventually made their way back to the states. Other early 20th century belt buckle manufacturers included Blackington, Anson, and Pioneer which produced small tongue-style buckles.
 Marshall, Chris. C J's Metal Detecting Pages, Buckles Through the Ages, 2002, web.archive.org/web/20101125185324/netmarshall.co.uk/buckletitlepage.htm.
 “Field Trip: Civil War Belt Buckles.” Antiques Roadshow, Public Broadcasting Service, 27 Apr. 2008, www.pbs.org/video/antiques-roadshow-field-segment-civil-war-belt-buckles/.
 Staff, Rochester Business Journal. “Beyond Rochester, He Left a Legacy of Leaders.” Rochester Business Journal, 26 Sept. 2008, rbj.net/2008/09/26/beyond-rochester-he-left-a-legacy-of-leaders/.