"...President Chase's inaugural was a grand affair, one full of promise. It would mark the high-water point of the Republican Party - inaugurated with substantial majorities in both houses, Chase entered office as perhaps the most experienced President in half a century, having served as a reformist Governor, a Senator, and a Secretary of the Treasury. Monetary questions were one of the dominant themes of the 1868 election and he had positioned himself as an expert, first for having managed the Treasury under Lincoln, leaving that office before the collapse in the currency at the conclusion of the war and then as a critic of the Seymour Treasury's vacillation between sound and soft money. Perhaps no President before or since Chase was as closely watchful of the Treasury, to be staffed by Massachusetts ally George Boutwell, and indeed it is an irony that Chase's background lay in monetary policy seeing as how his Presidency is now widely viewed as an economic disaster...
...the 41st Congress has been described as the "light in the dark," a moment of expanding liberty at the start of the Gilded Era that was marked more by reactionary politics than progressive ones. Chase left the relationship with Congress largely to his Attorney General Benjamin Wade, a former Senator from the President's home state of Ohio, who ably doled out patronage jobs within the civil service and judiciary. Wade's first priority, having been an ardent abolitionist, was to shepherd through Congress two laws, later to be codified as constitutional amendments, meant to overturn the Dred Scott decision. Though they felt confident in a 5-4 majority on the Davis Court [1] against the decision and that Justice Samuel Nelson would likely join them to overturn it as erroneous, and despite slavery only being practiced in two states, the resurgent Republicans were committed to abolishing the practice once and for all and defending the achievement from a future hostile Congressional majority or Supreme Court. The Civil Rights Act of 1869 explicitly stated that citizenship could not be denied on account of race and that slavery was hereby abolished throughout the states. With the immediate issue settled, Wade then helped shape with the help of Speaker Schuyler Colfax and Senator Charles Sumner the "Abolition Amendments," the 13th and 14th Amendments, the first of which abolished slavery and indentured servitude, the second of which conferred citizenship of the United States upon "all persons regardless of color, race or religion, and regardless of previous slavery or servitude," excepting Natives and foreign nationals, while also protecting the privileges and immunities of citizenship from interference by states and guaranteed due process from interference by states [2]. Both amendments passed, perhaps surprisingly, by two-thirds majorities, with only a handful of Democrats in the House and only Maryland's Senators voting against them, and their ratification by the states were done by the end of 1870. This great abolitionist victory, at long last, came on the heels of Conkling's Naval Act being passed both houses, again with a few Democratic defectors joining in, with a small tariff being raised to help fund the contracts for building the new steam frigates the expanded Navy would need. The 41st Congress also, at breakneck speed, passed a Specie Resumption Act to begin to gradually reduce the greenback supply by 1879, giving the Treasury a full decade to gradually deinflate the US money supply, viewed as a compromise between the sound and soft money factions of the Republican Party. It was one of the most productive Congresses in the history of the Republic up until that point, a working relationship so positive that Chase's appointment of Ebenezer Hoar to the Supreme Court to replace Robert Grier in late 1869 was settled after a mere 10 minutes of debate. The domestic front was, of course, calmer than the foreign one, where Chase and his Secretary of State Hamilton Fish faced a number of challenges..."
- The Republicans: A History (1989)
[1] Slight retcon - Lincoln promotes David Davis to be Chief Justice at the death of Roger B. Taney instead of Chase, an intraparty rival who he soured on at this point, and appoints Joseph Bradley as Davis's replacement as Associate Justice. That gives us, in 1869, a Supreme Court of David Davis (Lincoln), Joseph Bradley (Lincoln), Noah Swayne (Lincoln), Stephen Johnson Field (Lincoln), Samuel Freeman Miller (Lincoln), Samuel Nelson (Tyler), Robert Grier (Polk), Nathan Clifford (Buchanan), and William Strong (Seymour). Definitely a 5-4 majority against the Scott case, with Nelson a potential flip (he originally was supposed to write a narrower opinion for the majority until Taney flipped out over the dissents and took over) and Strong possibly a flip as well. Still, the abolitionists are not taking that risk with their lifelong goals at hand.
[2] Huge butterfly that "equal protection" not included in this version of the 14th, without Black Code southern states being reintegrated into the Union at forefront of people's minds. You'll also notice there's no 15th Amendment protecting voting rights here, either. Remember that this postwar Union is way more racist towards blacks than our own was... the priority for Republicans is really just to undo Dred Scott, protect that undoing from a future hostile Congress or Supreme Court, and nothing else.