WHY? We now know about the who [Clark County was named after, in response to the QoD on the subject], but why would the powers that be actually name a county after someone like William Clark? Was it named after he died? Did he buy someone off to get a county named after him? Seems like that would make an interesting QOD also.
As we saw in the previous QoD, Clark County was named after William Andrews Clark, the copper magnate, railroad builder, and U.S. senator from Montana.
Clark County's namesake played a key role in the development of the Las Vegas area in the early 1900s through his involvement in the San Pedro, Los Angeles & Salt Lake Railroad. He also founded the Las Vegas townsite in 1905 as a watering stop along his railroad line, auctioning off lots through the railroad company. So he can be considered one of the founding fathers of Las Vegas.
There's no definitive public record of any specific individual who proposed the name Clark County. And in fact, no evidence exists that Clark himself requested, lobbied for, or as you suggest bribe anyone to have the county named after him. Yes, he was alive at the time (he didn’t die until 1925), but he'd sold most of his interest in the San Pedro, Los Angeles & Salt Lake Railroad to Union Pacific by 1903, well before the county was created.
That happened six years later in 1909, when Clark County was split off from Lincoln County, which had encompassed the entire swath of southern Nevada. The new county went into effect in 1911.
So while he didn’t push for the honor and had largely exited the scene by the time the county was formed, William Clark's influence was still fresh and deeply appreciated by those shaping southern Nevada’s future. Naming the county after him was likely a way for Nevada legislators to recognize the transformational economic impact he had on the region, in terms of both infrastructure and growth, even if he was no longer active there.