Barbed wire
In this transition zone between the agricultural regions to the south and the rangeland to the north, conflict erupted, with vigilantes joining the scene causing chaos and even death. The Fence Cutting Wars ended with the passage of a Texas law in 1884 that made fence cutting a felony. Other states followed, although conflicts occurred through the early years of the 20th century. An 1885 federal law forbade placing such fences across the public domain.
Barbed wire is cited by historians as the invention that tamed the West. Herding large numbers of cattle on open range required significant manpower to catch strays. Barbed wire provided an inexpensive method to control the movement of cattle. By the beginning of the 20th century, large numbers of cowboys were unnecessary.

In the Southwest United States: John Warne Gates demonstrated barbed wire for Washburn and Moen in Military Plaza, San Antonio, Texas in 1876. The demonstration showing cattle restrained by the new kind of fencing was followed immediately by invitations to the Menger Hotel to place orders. Gates subsequently had a falling out with Washburn and Moen and Isaac Ellwood. He moved to St. Louis and founded the Southern Wire Company, which became the largest manufacturer of unlicensed or "bootleg" barbed wire.
An 1880 US District Court decision upheld the validity of the Glidden patent, effectively establishing a monopoly. This decision was affirmed by the US Supreme Court in 1892. In 1898 Gates took control of Washburn and Moen, and created the American Steel and Wire monopoly, which became a part of the United States Steel Corporation.
This led to disputes known as the range wars between open range ranchers and farmers in the late 19th century. These were similar to the disputes which resulted from enclosure laws in England in the early 18th century. These disputes were decisively settled in favor of the farmers, and heavy penalties were instituted for cutting a barbed wire fence. Within 2 years, nearly all of the open range had been fenced in under private ownership. For this reason, some historians have dated the end of the Old West era of American history to the invention and subsequent proliferation of barbed wire.

Installation: The most important and most time-consuming part of a barbed wire fence is constructing the corner post and the bracing assembly. A barbed wire fence is under tremendous tension, often up to half a ton, and so the corner post's sole function is to resist the tension of the fence spans connected to it. The bracing keeps the corner post vertical and prevents slack from developing in the fence.
Brace posts are placed in-line about 2.5 metres (8 ft) from the corner post. A horizontal compression brace connects the top of the two posts, and a diagonal wire connects the top of the brace post to the bottom of the corner post. This diagonal wire prevents the brace post from leaning, which in turn allows the horizontal brace to prevent the corner post from leaning into the brace post. A second set of brace posts (forming a double brace) is used whenever the barbed wire span exceeds 60 metres (200 ft).
When the barbed wire span exceeds 200 m (650 ft), a braced line assembly is added in-line. This has the function of a corner post and brace assembly but handles tension from opposite sides. It uses diagonal brace wire that connects the tops to the bottoms of all adjacent posts.
Line posts are installed along the span of the fence at intervals of 2.5 to 15 m (8 to 50 ft). An interval of 5 m (16 ft) is most common. Heavy livestock and crowded pasture demands the smaller spacing. The sole function of a line post is not to take up slack but to keep the barbed wire strands spaced equally and off the ground.
Once these posts and bracing have been erected, the wire is wrapped around one corner post, held with a hitch (a timber hitch works well for this) often using a staple to hold the height and then reeled out along the span of the fence replacing the roll every 400 m. It is then wrapped around the opposite corner post, pulled tightly with wire stretchers, and sometimes nailed with more fence staples, although this may make readjustment of tension or replacement of the wire more difficult. Then it is attached to all of the line posts with fencing staples driven in partially to allow stretching of the wire.
There are several ways to anchor the wire to a corner post:

Hand-knotting. The wire is wrapped around the corner post and knotted by hand. This is the most common method of attaching wire to a corner post. A timber hitch works well as it stays better with wire than with rope.
Crimp sleeves. The wire is wrapped around the corner post and bound to the incoming wire using metal sleeves which are crimped using lock cutters. This method should be avoided because while sleeves can work well on repairs in the middle of the fence where there is not enough wire for hand knotting, they tend to slip when under tension.
Wire vise. The wire is passed through a hole drilled into the corner post and is anchored on the far side.
Wire wrap. The wire is wrapped around the corner post and wrapped onto a special, gritted helical wire which also wraps around the incoming wire, with friction holding it in place.
Barbed wire for agriculture use is typically double-strand 12+1⁄2-gauge, zinc-coated (galvanized) steel and comes in rolls of 400 m (1,320 ft) length. Barbed wire is usually placed on the inner (pasture) side of the posts. Where a fence runs between two pastures livestock could be with the wire on the outside or on both sides of the fence.
Galvanized wire is classified into three categories; Classes I, II, and III. Class I has the thinnest coating and the shortest life expectancy. A wire with Class I coating will start showing general rusting in 8 to 10 years, while the same wire with Class III coating will show rust in 15 to 20 years. Aluminum-coated wire is occasionally used, and yields a longer life.
Corner posts are 15 to 20 centimetres (6 to 8 in) in diameter or larger, and a minimum 2.5 metres (8 ft) in length may consist of treated wood or from durable on-site trees such as osage orange, black locust, red cedar, or red mulberry, also railroad ties, telephone, and power poles are salvaged to be used as corner posts (poles and railroad ties were often treated with chemicals determined to be an environmental hazard and cannot be reused in some jurisdictions). In Canada spruce posts are sold for this purpose. Posts are 10 centimetres (4 in) in diameter driven at least 1.2 metres (4 ft) and may be anchored in a concrete base 51 centimetres (20 in) square and 110 centimetres (42 in) deep. Iron posts, if used, are a minimum 64 millimetres (2.5 in) in diameter. Bracing wire is typically smooth 9-gauge. Line posts are set to a depth of about 76 centimetres (30 in). Conversely, steel posts are not as stiff as wood, and wires are fastened with slips along fixed teeth, which means variations in driving height affect wire spacing.
During the First World War, screw pickets were used for the installation of wire obstacles; these were metal rods with eyelets for holding strands of wire, and a corkscrew-like end that could literally be screwed into the ground rather than hammered, so that wiring parties could work at night near enemy soldiers and not reveal their position by the sound of hammers.

Gates: As with any fence, barbed wire fences require gates to allow the passage of persons, vehicles and farm implements. Gates vary in width from 3.5 metres (12 ft) to allow the passage of vehicles and tractors, to 12 metres (40 ft) on farm land to pass combines and swathers.
One style of gate is called the Hampshire gate in the UK, a New Zealand gate in some areas, and often simply a "gate" elsewhere. Made of wire with posts attached at both ends and in the middle, it is permanently wired on one side and attaches to a gate post with wire loops on the other. Most designs can be opened by hand, though some gates that are frequently opened and closed may have a lever attached to assist in bringing the upper wire loop over the gate post.
Gates for cattle tend to have four wires when along a three wire fence, as cattle tend to put more stress on gates, particularly on corner gates. The fence on each side of the gate ends with two corner posts braced or unbraced depending on the size of the post. An unpounded post (often an old broken post) is held to one corner post with wire rings which act as hinges. On the other end a full-length post, the tractor post, is placed with the pointed end upwards with a ring on the bottom stapled to the other corner post, the latch post, and on top a ring is stapled to the tractor post, tied with a Stockgrower's Lash or one of numerous other opening bindings. Wires are then tied around the post at one end then run to the other end where they are stretched by hand or with a stretcher, before posts are stapled on every 1.2 metres (4 ft).