Whiteside v. Haselton & Others was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of mandamus to a county court. The case arose when the plaintiff, Whiteside, sought to have the county court issue a writ of mandamus to compel the defendants, Haselton and others, to pay him a debt. The defendants argued that the state court did not have the authority to issue the writ of mandamus. The Supreme Court held that the state court did have the authority to issue the writ of mandamus. The Court reasoned that the state court had the power to issue the writ of mandamus because it was a court of general jurisdiction and the writ of mandamus was a proper remedy for the plaintiff's claim. The Court also noted that the writ of mandamus was a proper remedy because it was necessary to compel the defendants to pay the debt. In conclusion, the Supreme Court held that the state court had the authority to issue the writ of mandamus to compel the defendants to pay the debt. The Court reasoned that the writ of mandamus was a proper remedy for the plaintiff's claim and was necessary to compel the defendants to pay the debt.

Justice Field delivered the dissenting opinion in Whiteside v. Haselton & Others, arguing that the majority had incorrectly interpreted and applied a provision of Oregon law to reach its decision. He argued that under Oregon's Constitution, only those who were citizens of the state at the time it was adopted could be considered "original settlers" for purposes of claiming land grants from Congress. The majority had instead held that any person who arrived in Oregon before 1859 would qualify as an original settler regardless of their citizenship status when they arrived or when the constitution was adopted. Justice Field disagreed with this interpretation, noting that such a broad definition would allow non-citizens to benefit from privileges reserved exclusively for citizens by ignoring both constitutional language and legislative intent behind it. He concluded by stating his belief that allowing non-citizens to claim these benefits violated both federal and state laws regarding land grants and should not have been allowed by either court below or affirmed on appeal by the Supreme Court itself.