The St. Louis Brown Stockings have the best ERA by a team in a season, with an ERA of 1.22 in 1876.

	TEAM	ERA	SEASON	G	W%	W	L	GS	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Brown Stockings	1.22	1876	64	.703	45	19	64	103	63		0	577.0	472	78	229	3	39		2,283	34	1.61	0.61	2.64	0.05	4.5	1.7	0.89		3.57	7.36
2	Grays	1.61	1884	114	.750	84	28	114	639	107		3	1036.1	825	185	388	26	172		4,123	70	5.55	1.49	3.72	0.23	15.5	4.2	0.96		3.37	7.16
3	Grays	1.64	1880	87	.619	52	32	87	286	75		3	799.0	663	146	299	7	51		3,137	26	3.22	0.57	5.61	0.08	9.1	1.6	0.89		3.37	7.47
4	Red Stockings	1.65	1882	80	.688	55	25	80	165	77		0	721.1	609	132	268	7	125		2,977	34	2.06	1.56	1.32	0.09	5.5	4.2	1.02		3.34	7.60
5	Dark Blues	1.67	1876	69	.691	47	21	69	114	69		0	624.0	570	116	261	2	27		2,536	15	1.64	0.39	4.22	0.03	4.5	1.1	0.96		3.76	8.22
6	Grays	1.69	1876	69	.455	30	36	69	125	67		0	643.0	605	121	344	3	38		2,680	25	1.75	0.53	3.29	0.04	4.7	1.4	1.00		4.81	8.47
7	Gothams	1.72	1885	112	.759	85	27	112	516	109		1	994.0	758	190	370	11	265		3,962	77	4.67	2.40	1.95	0.10	13.0	6.7	1.03		3.35	6.86
8	Cubs	1.73	1907	155	.704	107	45	155	586	114	31	8	1373.1	1,054	264	390	11	402	38	5,315	25	3.84	2.63	1.46	0.07	11.0	7.6	1.06	.244	2.56	6.91
9	Cubs	1.74	1909	155	.680	104	49	155	680	111	32	11	1409.1	1,094	272	389	6	364	38	5,494	30	4.34	2.32	1.87	0.04	12.4	6.6	1.03	.247	2.48	6.99
10	Cubs	1.75	1906	155	.763	116	36	155	702	125	28	10	1388.1	1,018	270	381	12	446	53	5,427	20	4.55	2.89	1.57	0.08	12.9	8.2	1.05	.239	2.47	6.60
11	White Stockings	1.76	1876	66	.788	52	14	66	51	58		4	592.1	608	116	257	6	29		2,489	3	0.77	0.44	1.76	0.09	2.0	1.2	1.08		3.90	9.24
12	Athletics	1.79	1910	155	.680	102	48	155	789	123	24	5	1421.2	1,103	282	441	8	450	55	5,503	39	4.99	2.85	1.75	0.05	14.3	8.2	1.09	.261	2.79	6.98
13	Reds	1.84	1878	61	.617	37	23	61	220	61		0	548.0	546	112	281	2	63		2,267	43	3.61	1.03	3.49	0.03	9.7	2.8	1.11		4.61	8.97
14	Blues	1.90	1880	85	.560	47	37	85	289	83		1	759.2	685	160	337	4	98		3,100	31	3.42	1.16	2.95	0.05	9.3	3.2	1.03		3.99	8.12
15	White Stockings	1.93	1880	86	.798	67	17	86	367	80		3	775.0	622	166	317	8	129		3,102	33	4.26	1.50	2.84	0.09	11.8	4.2	0.97		3.68	7.22
16	Athletics	1.93	1909	153	.621	95	58	153	728	110	27	3	1378.0	1,069	296	416	9	386	65	5,385	31	4.75	2.52	1.89	0.06	13.5	7.2	1.06	.253	2.72	6.98
17	Maroons	1.96	1884	114	.832	94	19	114	550	104		6	993.0	838	216	429	9	110		4,038	52	4.98	1.00	5.00	0.08	13.6	2.7	0.95		3.89	7.60
18	Giants	1.96	1888	138	.641	84	47	138	726	133		1	1208.0	907	263	479	27	307	37	4,897	65	5.41	2.29	2.36	0.20	14.8	6.3	1.00	.232	3.57	6.76
19	White Sox	1.99	1905	158	.605	92	60	158	613	131	15	0	1427.0	1,163	315	450	11	329	31	5,542	39	3.87	2.07	1.86	0.07	11.1	5.9	1.05	.253	2.84	7.33
20	Naps	2.02	1908	157	.584	90	64	157	548	108	18	5	1424.1	1,172	319	459	16	328	34	5,488	24	3.46	2.07	1.67	0.10	10.0	6.0	1.05	.253	2.90	7.41
21	Colonels	2.03	1882	80	.525	42	38	80	240	73		0	693.1	637	156	352	6	112		2,904	47	3.12	1.45	2.14	0.08	8.3	3.9	1.08		4.57	8.27
22	White Sox	2.03	1910	156	.444	68	85	156	785	103	23	7	1421.0	1,130	320	479	16	381	38	5,513	31	4.97	2.41	2.06	0.10	14.2	6.9	1.06	.259	3.03	7.16
23	Cubs	2.04	1905	155	.601	92	61	155	627	133	23	2	1407.1	1,135	319	442	14	385	51	5,500	21	4.01	2.46	1.63	0.09	11.4	7.0	1.08	.253	2.83	7.26
24	White Sox	2.05	1909	159	.513	78	74	159	669	115	26	4	1430.1	1,182	326	464	8	340	52	5,560	29	4.21	2.14	1.97	0.05	12.0	6.1	1.06	.261	2.92	7.44
25	Pirates	2.07	1909	154	.724	110	42	154	490	93	21	11	1401.2	1,174	322	448	12	320	48	5,438	14	3.15	2.05	1.53	0.08	9.0	5.9	1.07	.254	2.88	7.54