Before the Industrial Revolution, selling was merely a sideline of the people who created products or offered services. There was no separate sales force. Almost all sales transactions occurred on a small scale and at the local level. Few products were shipped long distances and those that were, such as spices from the East, were bought from merchants who had purchased them and transported them from their source.

The Industrial Revolution provided not only large-scale output of manufactured goods but also the distribution network of the railroads, which made it possible for manufacturers to sell goods directly to customers in distant cities: retail stores for consumer products and other businesses for various kinds of goods. As the market grew, wholesalers set up businesses to act as intermediaries between the producers and the local sellers. The expanded market allowed for unprecedented volumes of sales, but distant producers lacked the personal connection to local consumers that local producers had previously enjoyed. The occupation of sales workers thus emerged to restore this personal connection between mass producers and distant buyers. (One exception among the mass producers was the farmers, whose output now became undifferentiated commodities.)

At first, sales workers learned their trade informally. One of the first attempts to conduct sales training formally was in 1885, when National Cash Register created a sales manual for its distributors and held a training session at a trade show in 1885. In the early decades of the 20th century, the training programs that companies developed for their sales staffs focused on building friendly relationships so customers would make repeated purchases. However, as an increasingly urban culture created opportunities for door-to-door sales workers, high-pressure, closing-oriented sales techniques began to gain currency. This style influenced a 1977 book called How to Sell Anything to Anybody, written by a highly successful sales worker named Joe Girard and claiming to teach universal principles governing the sales process. In subsequent decades, more subtle techniques involving empathy and relationship-building came back into favor.

Technology has been a two-edged sword for the sales industry. Some technologies have threatened sales workers by allowing producers or wholesalers to contact distant buyers directly and thus bypass the sales force. The first technology of this kind was the mail-order catalogue, pioneered by Aaron Montgomery Ward of Chicago in 1872. The next major disruption was e-commerce, facilitated by the World Wide Web. For example, many jobs for travel agents have been eliminated by Web sites that allow travelers to compare fares and accommodation costs, read crowdsourced reviews of travel options, and book flights and hotel stays.

On the other hand, technology has given sales workers one of their greatest tools, the telephone, which has created an entirely new sales occupation: telemarketers. These workers use the telephone to conduct every phase of the sales process—with the exception of prospecting, usually done by a computer working from a database. More traditional sales workers also use the telephone to contact customers for various phases of sales, as well as employers for the latest information about products and services. Some of the technologies that accompany the telephone are helpful for sales, such as voicemail; others, such as caller ID, can create obstacles. Another obstacle can be the Do Not Call Registry, a Federal Trade Commission law enacted in 2003. People who don't want to hear from telemarketers submit the telemarketers' phone numbers to the registry and the telemarketers are expected to comply.

Sales workers are also taking advantage of computer technologies. They use databases to turn up prospects. Social networks and Twitter also serve this purpose and can help build long-term relationships with customers. E-mail and texting, now available on smartphones, can sometimes be more convenient modes of communication than the voice telephone. Software for customer relationship management (CRM) has been developed to span several of these database and communications functions.

Presentation software such as PowerPoint now allows people with modest graphic skills to achieve impressive effects. Conferencing programs allow sales workers to conduct virtual sales presentations from a distance, and video hosting sites such as YouTube make it easy to distribute videos of product demonstrations. On the road, sales workers use high-tech tools to plan trips and navigate using GPS.