The History of Bookmaking: From Ancient Rome to Modern Sportsbooks
People have been laying odds on outcomes for about two thousand years. The tech changes. The math does not. Here is the abridged version for people who actually bet.
Bookmaking is older than football, older than horse racing, older than the concept of the stadium. It goes back to Rome at minimum, possibly further. My thesis: every so-called innovation in modern sportsbooks (live betting, cash out, bet builders) is a re-skin of something bookmakers were doing in the eighteenth century. The math is the same. The UI is new.
Second paragraph, the point of this piece: if you understand how the edge has always worked, you stop being impressed by marketing and start focusing on the things that actually change your expected return.
Rome to the racetrack
Ancient Romans bet on gladiator combats and chariot races. The historical record is thin on whether there was organized bookmaking in the modern sense, but informal laying of odds existed. Juvenal's Satires complain about Roman crowds obsessing over the Circus Maximus and the money changing hands around it. This is, at a minimum, informal betting infrastructure.
The first documented bookmaker in a sense we would recognize is Harry Ogden, an English racing man who started laying odds on horses at Newmarket in 1795. Before Ogden, betting on horse races was bettor-versus-bettor, matched privately. Ogden's innovation was to offer odds on every horse in a race simultaneously, with an overround built in, so that regardless of which horse won, he collected on some bets and paid on others. This is the same model every fixed-odds bookmaker still uses today.
The overround, that extra percentage above 100 that lets the book profit on balanced action, is the single most important concept in bookmaking and Ogden invented its practical application. Every casino, every sportsbook, every prop market operates on overround. The number has changed (modern digital sportsbooks run 2 to 8 percent margins depending on market depth) but the mechanism is unchanged.
The 19th century professionalization
British bookmaking went legitimate and then semi-legitimate across the 1800s. On-course bookmaking at racetracks was tolerated. Off-course cash betting was illegal but ubiquitous, operated through networks of "bookies' runners" and back-room establishments. The 1853 Betting Houses Act banned off-course betting in Britain; it remained underground until the 1961 Betting and Gaming Act brought it above ground with the establishment of licensed betting shops.
America's path was different. Horse racing bookmaking was common in the late 1800s, then progressively outlawed during the Progressive Era. By the 1910s bookmaking on horse racing was illegal in most states, and the pari-mutuel system (invented by Pierre Oller in France in the 1860s) became the dominant legal model: bettors bet against each other into a pool, and the track takes a percentage off the top. Pari-mutuel is not bookmaking; it is a different structure entirely. It shaped American gambling culture through most of the 20th century.
The Vegas era
When Nevada legalized gambling in 1931, sports betting was explicitly included, but the market did not take off until much later. The sports book at the Stardust, run by Frank Rosenthal in the 1970s, was the first modern high-volume sportsbook in the US, setting lines that other books across the country would reference. Rosenthal's work brought the concept of a central "line" (the consensus spread) into American sports betting.
Before Rosenthal, point spreads existed (invented by Charles McNeil in Chicago in the 1940s, possibly borrowed from a bookmaker named Ed Curd in Kentucky) but the coordination between books was informal. After Rosenthal, Vegas books moved in near-lockstep, and the Nevada sportsbook became the reference point for the underground US market as well.
The internet era
Online sportsbooks emerged in the mid-1990s, initially licensed out of Antigua and Costa Rica. Pinnacle Sports opened in 1998 and pioneered the low-margin, high-volume model: offering tighter prices (lower overround) on the assumption that sharper pricing would attract professional volume. Pinnacle, Betfair (which launched exchange betting in 2000), and a few other operators effectively created the modern online sports betting market.
Betfair's exchange model deserves a specific mention. Betfair is not a bookmaker; it is a peer-to-peer exchange where users lay and back odds against each other, with Betfair taking a commission. This is a structural change: there is no book with an exposure, there are only other users. Exchange pricing is generally sharper than sportsbook pricing, and professional bettors often use exchange prices as a reference for what the "true" odds are on a market.
The modern product
Today's sportsbook is a combination of Harry Ogden's overround, Rosenthal's shared line, Pinnacle's low-margin volume model, and a suite of user-interface innovations that are mostly marketing rather than mathematics.
Live betting (betting on a game in progress) is old. Bookmakers have been taking in-running bets on horse races for over a century. The innovation is the speed at which lines are recalculated (milliseconds rather than seconds), and the number of markets offered (hundreds per game rather than a few).
Cash out is old. Bookmakers have been buying out positions for as long as there have been positions. The innovation is that the modern app automates it. The math is unchanged: the book's cash-out price is always worse for you than the fair buyout, because the book builds a second overround into the transaction.
Bet builders (same-game parlays) are old. Multi-selection accumulators have been offered by British bookmakers since the mid-1900s. The innovation is that bet builders on correlated outcomes (selections from the same game) are now priced using models that partly capture the correlation, rather than being outright banned. The books still price them favorably for themselves.
The unchanging core
What every bookmaker has always needed to do: offer odds on every outcome such that the implied probabilities sum to more than 100 percent, manage exposure when action imbalances, and identify which customers are sharp (so they can limit those accounts) and which are recreational (so they can cultivate those accounts). This is exactly what Harry Ogden was doing at Newmarket in 1795. The software has changed. The job has not.
For a bettor, the practical takeaway: do not get distracted by the product innovations the operator markets at you. The math of the overround is what determines your long-run return. A 2 percent margin is meaningfully better for you than a 6 percent margin, and every feature that wraps the underlying wager in more UI (live betting, cash out, bet builder) is a place where the operator inserts additional margin. The more clicks between your view and your bet, the more the book charges for the service.
The core skill is the same skill it has always been: identifying markets where your estimate of the true probability differs from the implied probability by more than the margin, and betting those specifically. Nothing about the internet era changed that. The internet just made it faster to spot them and faster to get limited when you do.